Petya loves lucky numbers. Everybody knows that lucky numbers are positive integers whose decimal representation contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.

Let *next*(*x*) be the minimum lucky number which is larger than or equals *x*. Petya is interested what is the value of the expression *next*(*l*) + *next*(*l* + 1) + ... + *next*(*r* - 1) + *next*(*r*). Help him solve this problem.
The single line contains two integers *l* and *r* (1 ≤ *l* ≤ *r* ≤ 10<sup class="upper-index">9</sup>) — the left and right interval limits.
2 7
33
7 7
7
1 9
125
4 7
25
12 47
1593
6 77
4012
1 100
14247
1000000000 1000000000
4444444444
77 77
77
69 788
452195
474 747
202794
4 77777
4070145675
1 1000000
1394675359387
47 744447
381286992761
47444 1000000000
1394672348253941136
48 854888
749733199853
854444 985555
582719941728
774744 774747
3098985
654 987654
1339803940266
477777 1000000000
1394672167300009765
77777 777777777
407018021649898097
963 85555574
7526978888069560
47 7444
38125896
1 1000000000
1394672350065645019
474 999888555
1394177038954402791
777 1000000000
1394672350065239125
7 777777774
407018023386632646
369 852
606732
47 47
47
747 748
1521
77777440 77777444
388887220
987545885 999875584
54798666661186800
2 777777776
407018024942188226
1 1
4
1 2
8
999999999 1000000000
8888888888
777777777 1000000000
987654325123456789
777777778 1000000000
987654324345679012
5 6
14
49 49
74
6 6
7
3 4
8
import os
import sys
from io import BytesIO, IOBase

_str = str
str = lambda x = b"": x if type(x) is bytes else _str(x).encode()

BUFSIZE = 8192
class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._file = file
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)

class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")

sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
input = lambda: sys.stdin.readline().rstrip("\r\n")
mi = lambda: map(int, input().split())
fi = lambda: map(float, input().split())
si = lambda: input().split()
ii = lambda: int(input())
li = lambda: list(mi())

ret = ['4', '7', '44', '47', '74', '77', '444', '447', '474', '477', '744', '747', '774', '777', '4444', '4447', '4474', '4477', '4744', '4747', '4774', '4777', '7444', '7447', '7474', '7477', '7744', '7747', '7774', '7777', '44444', '44447', '44474', '44477', '44744', '44747', '44774', '44777', '47444', '47447', '47474', '47477', '47744', '47747', '47774', '47777', '74444', '74447', '74474', '74477', '74744', '74747', '74774', '74777', '77444', '77447', '77474', '77477', '77744', '77747', '77774', '77777', '444444', '444447', '444474', '444477', '444744', '444747', '444774', '444777', '447444', '447447', '447474', '447477', '447744', '447747', '447774', '447777', '474444', '474447', '474474', '474477', '474744', '474747', '474774', '474777', '477444', '477447', '477474', '477477', '477744', '477747', '477774', '477777', '744444', '744447', '744474', '744477', '744744', '744747', '744774', '744777', '747444', '747447', '747474', '747477', '747744', '747747', '747774', '747777', '774444', '774447', '774474', '774477', '774744', '774747', '774774', '774777', '777444', '777447', '777474', '777477', '777744', '777747', '777774', '777777', '4444444', '4444447', '4444474', '4444477', '4444744', '4444747', '4444774', '4444777', '4447444', '4447447', '4447474', '4447477', '4447744', '4447747', '4447774', '4447777', '4474444', '4474447', '4474474', '4474477', '4474744', '4474747', '4474774', '4474777', '4477444', '4477447', '4477474', '4477477', '4477744', '4477747', '4477774', '4477777', '4744444', '4744447', '4744474', '4744477', '4744744', '4744747', '4744774', '4744777', '4747444', '4747447', '4747474', '4747477', '4747744', '4747747', '4747774', '4747777', '4774444', '4774447', '4774474', '4774477', '4774744', '4774747', '4774774', '4774777', '4777444', '4777447', '4777474', '4777477', '4777744', '4777747', '4777774', '4777777', '7444444', '7444447', '7444474', '7444477', '7444744', '7444747', '7444774', '7444777', '7447444', '7447447', '7447474', '7447477', '7447744', '7447747', '7447774', '7447777', '7474444', '7474447', '7474474', '7474477', '7474744', '7474747', '7474774', '7474777', '7477444', '7477447', '7477474', '7477477', '7477744', '7477747', '7477774', '7477777', '7744444', '7744447', '7744474', '7744477', '7744744', '7744747', '7744774', '7744777', '7747444', '7747447', '7747474', '7747477', '7747744', '7747747', '7747774', '7747777', '7774444', '7774447', '7774474', '7774477', '7774744', '7774747', '7774774', '7774777', '7777444', '7777447', '7777474', '7777477', '7777744', '7777747', '7777774', '7777777', '44444444', '44444447', '44444474', '44444477', '44444744', '44444747', '44444774', '44444777', '44447444', '44447447', '44447474', '44447477', '44447744', '44447747', '44447774', '44447777', '44474444', '44474447', '44474474', '44474477', '44474744', '44474747', '44474774', '44474777', '44477444', '44477447', '44477474', '44477477', '44477744', '44477747', '44477774', '44477777', '44744444', '44744447', '44744474', '44744477', '44744744', '44744747', '44744774', '44744777', '44747444', '44747447', '44747474', '44747477', '44747744', '44747747', '44747774', '44747777', '44774444', '44774447', '44774474', '44774477', '44774744', '44774747', '44774774', '44774777', '44777444', '44777447', '44777474', '44777477', '44777744', '44777747', '44777774', '44777777', '47444444', '47444447', '47444474', '47444477', '47444744', '47444747', '47444774', '47444777', '47447444', '47447447', '47447474', '47447477', '47447744', '47447747', '47447774', '47447777', '47474444', '47474447', '47474474', '47474477', '47474744', '47474747', '47474774', '47474777', '47477444', '47477447', '47477474', '47477477', '47477744', '47477747', '47477774', '47477777', '47744444', '47744447', '47744474', '47744477', '47744744', '47744747', '47744774', '47744777', '47747444', '47747447', '47747474', '47747477', '47747744', '47747747', '47747774', '47747777', '47774444', '47774447', '47774474', '47774477', '47774744', '47774747', '47774774', '47774777', '47777444', '47777447', '47777474', '47777477', '47777744', '47777747', '47777774', '47777777', '74444444', '74444447', '74444474', '74444477', '74444744', '74444747', '74444774', '74444777', '74447444', '74447447', '74447474', '74447477', '74447744', '74447747', '74447774', '74447777', '74474444', '74474447', '74474474', '74474477', '74474744', '74474747', '74474774', '74474777', '74477444', '74477447', '74477474', '74477477', '74477744', '74477747', '74477774', '74477777', '74744444', '74744447', '74744474', '74744477', '74744744', '74744747', '74744774', '74744777', '74747444', '74747447', '74747474', '74747477', '74747744', '74747747', '74747774', '74747777', '74774444', '74774447', '74774474', '74774477', '74774744', '74774747', '74774774', '74774777', '74777444', '74777447', '74777474', '74777477', '74777744', '74777747', '74777774', '74777777', '77444444', '77444447', '77444474', '77444477', '77444744', '77444747', '77444774', '77444777', '77447444', '77447447', '77447474', '77447477', '77447744', '77447747', '77447774', '77447777', '77474444', '77474447', '77474474', '77474477', '77474744', '77474747', '77474774', '77474777', '77477444', '77477447', '77477474', '77477477', '77477744', '77477747', '77477774', '77477777', '77744444', '77744447', '77744474', '77744477', '77744744', '77744747', '77744774', '77744777', '77747444', '77747447', '77747474', '77747477', '77747744', '77747747', '77747774', '77747777', '77774444', '77774447', '77774474', '77774477', '77774744', '77774747', '77774774', '77774777', '77777444', '77777447', '77777474', '77777477', '77777744', '77777747', '77777774', '77777777', '444444444', '444444447', '444444474', '444444477', '444444744', '444444747', '444444774', '444444777', '444447444', '444447447', '444447474', '444447477', '444447744', '444447747', '444447774', '444447777', '444474444', '444474447', '444474474', '444474477', '444474744', '444474747', '444474774', '444474777', '444477444', '444477447', '444477474', '444477477', '444477744', '444477747', '444477774', '444477777', '444744444', '444744447', '444744474', '444744477', '444744744', '444744747', '444744774', '444744777', '444747444', '444747447', '444747474', '444747477', '444747744', '444747747', '444747774', '444747777', '444774444', '444774447', '444774474', '444774477', '444774744', '444774747', '444774774', '444774777', '444777444', '444777447', '444777474', '444777477', '444777744', '444777747', '444777774', '444777777', '447444444', '447444447', '447444474', '447444477', '447444744', '447444747', '447444774', '447444777', '447447444', '447447447', '447447474', '447447477', '447447744', '447447747', '447447774', '447447777', '447474444', '447474447', '447474474', '447474477', '447474744', '447474747', '447474774', '447474777', '447477444', '447477447', '447477474', '447477477', '447477744', '447477747', '447477774', '447477777', '447744444', '447744447', '447744474', '447744477', '447744744', '447744747', '447744774', '447744777', '447747444', '447747447', '447747474', '447747477', '447747744', '447747747', '447747774', '447747777', '447774444', '447774447', '447774474', '447774477', '447774744', '447774747', '447774774', '447774777', '447777444', '447777447', '447777474', '447777477', '447777744', '447777747', '447777774', '447777777', '474444444', '474444447', '474444474', '474444477', '474444744', '474444747', '474444774', '474444777', '474447444', '474447447', '474447474', '474447477', '474447744', '474447747', '474447774', '474447777', '474474444', '474474447', '474474474', '474474477', '474474744', '474474747', '474474774', '474474777', '474477444', '474477447', '474477474', '474477477', '474477744', '474477747', '474477774', '474477777', '474744444', '474744447', '474744474', '474744477', '474744744', '474744747', '474744774', '474744777', '474747444', '474747447', '474747474', '474747477', '474747744', '474747747', '474747774', '474747777', '474774444', '474774447', '474774474', '474774477', '474774744', '474774747', '474774774', '474774777', '474777444', '474777447', '474777474', '474777477', '474777744', '474777747', '474777774', '474777777', '477444444', '477444447', '477444474', '477444477', '477444744', '477444747', '477444774', '477444777', '477447444', '477447447', '477447474', '477447477', '477447744', '477447747', '477447774', '477447777', '477474444', '477474447', '477474474', '477474477', '477474744', '477474747', '477474774', '477474777', '477477444', '477477447', '477477474', '477477477', '477477744', '477477747', '477477774', '477477777', '477744444', '477744447', '477744474', '477744477', '477744744', '477744747', '477744774', '477744777', '477747444', '477747447', '477747474', '477747477', '477747744', '477747747', '477747774', '477747777', '477774444', '477774447', '477774474', '477774477', '477774744', '477774747', '477774774', '477774777', '477777444', '477777447', '477777474', '477777477', '477777744', '477777747', '477777774', '477777777', '744444444', '744444447', '744444474', '744444477', '744444744', '744444747', '744444774', '744444777', '744447444', '744447447', '744447474', '744447477', '744447744', '744447747', '744447774', '744447777', '744474444', '744474447', '744474474', '744474477', '744474744', '744474747', '744474774', '744474777', '744477444', '744477447', '744477474', '744477477', '744477744', '744477747', '744477774', '744477777', '744744444', '744744447', '744744474', '744744477', '744744744', '744744747', '744744774', '744744777', '744747444', '744747447', '744747474', '744747477', '744747744', '744747747', '744747774', '744747777', '744774444', '744774447', '744774474', '744774477', '744774744', '744774747', '744774774', '744774777', '744777444', '744777447', '744777474', '744777477', '744777744', '744777747', '744777774', '744777777', '747444444', '747444447', '747444474', '747444477', '747444744', '747444747', '747444774', '747444777', '747447444', '747447447', '747447474', '747447477', '747447744', '747447747', '747447774', '747447777', '747474444', '747474447', '747474474', '747474477', '747474744', '747474747', '747474774', '747474777', '747477444', '747477447', '747477474', '747477477', '747477744', '747477747', '747477774', '747477777', '747744444', '747744447', '747744474', '747744477', '747744744', '747744747', '747744774', '747744777', '747747444', '747747447', '747747474', '747747477', '747747744', '747747747', '747747774', '747747777', '747774444', '747774447', '747774474', '747774477', '747774744', '747774747', '747774774', '747774777', '747777444', '747777447', '747777474', '747777477', '747777744', '747777747', '747777774', '747777777', '774444444', '774444447', '774444474', '774444477', '774444744', '774444747', '774444774', '774444777', '774447444', '774447447', '774447474', '774447477', '774447744', '774447747', '774447774', '774447777', '774474444', '774474447', '774474474', '774474477', '774474744', '774474747', '774474774', '774474777', '774477444', '774477447', '774477474', '774477477', '774477744', '774477747', '774477774', '774477777', '774744444', '774744447', '774744474', '774744477', '774744744', '774744747', '774744774', '774744777', '774747444', '774747447', '774747474', '774747477', '774747744', '774747747', '774747774', '774747777', '774774444', '774774447', '774774474', '774774477', '774774744', '774774747', '774774774', '774774777', '774777444', '774777447', '774777474', '774777477', '774777744', '774777747', '774777774', '774777777', '777444444', '777444447', '777444474', '777444477', '777444744', '777444747', '777444774', '777444777', '777447444', '777447447', '777447474', '777447477', '777447744', '777447747', '777447774', '777447777', '777474444', '777474447', '777474474', '777474477', '777474744', '777474747', '777474774', '777474777', '777477444', '777477447', '777477474', '777477477', '777477744', '777477747', '777477774', '777477777', '777744444', '777744447', '777744474', '777744477', '777744744', '777744747', '777744774', '777744777', '777747444', '777747447', '777747474', '777747477', '777747744', '777747747', '777747774', '777747777', '777774444', '777774447', '777774474', '777774477', '777774744', '777774747', '777774774', '777774777', '777777444', '777777447', '777777474', '777777477', '777777744', '777777747', '777777774', '777777777', '4444444444']
def cal(lp):
    back = 0
    f = 0
    if lp == 0: return 0
    for x in range(len(ret)):
        if int(ret[x]) > lp: 
            f += (lp - back) * int(ret[x])
            break
        f += (int(ret[x]) - back) * int(ret[x])
        back = int(ret[x])
    return f

l, r = mi()
print(cal(r) - cal(l - 1))