Theatre Square in the capital city of Berland has a rectangular shape with the size *n* × *m* meters. On the occasion of the city's anniversary, a decision was taken to pave the Square with square granite flagstones. Each flagstone is of the size *a* × *a*.

What is the least number of flagstones needed to pave the Square? It's allowed to cover the surface larger than the Theatre Square, but the Square has to be covered. It's not allowed to break the flagstones. The sides of flagstones should be parallel to the sides of the Square.
The input contains three positive integer numbers in the first line: *n*,  *m* and *a* (1 ≤  *n*, *m*, *a* ≤ 10<sup class="upper-index">9</sup>).
6 6 4
4
1 1 1
1
2 1 1
2
1 2 1
2
2 2 1
4
2 1 2
1
1 1 3
1
2 3 4
1
1000000000 1000000000 1
1000000000000000000
12 13 4
12
222 332 5
3015
1000 1000 10
10000
1001 1000 10
10100
100 10001 1000000000
1
1000000000 1000000000 1000000000
1
1000000000 1000000000 999999999
4
1000000000 1000000000 192
27126743055556
1000000000 987654321 1
987654321000000000
456784567 1000000000 51
175618850864484
39916800 134217728 40320
3295710
import os
import sys
from bisect import bisect_left as bl, bisect_right as br, bisect
from collections import defaultdict as dd, deque, Counter
from heapq import merge, heapify, heappop, heappush, nsmallest
from itertools import combinations
from math import ceil, floor, gcd, fabs, factorial, fmod, sqrt, inf, log
from io import BytesIO, IOBase

MOD  = 1_000_000_007
MOD2 = 998244353
PI   = 3.1415926535897932384626433832795028841971693993751058209749446

# region fastio
BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, 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)
# endregion

# input str
def inp():
    return sys.stdin.readline().strip()

# input int
def iinp():
    return int(inp())

# map and array of int
def mp():
    return map(int, inp().split())

def liinp():
    return list(mp())

# array of string/char
def lmps():
    return list(map(str, inp()))

# dp
def l1d(n, val=0):
    return [val for i in range(n)]  # dp[i]

def l2d(n, m, val=0):
    return [l1d(m, val) for j in range(n)]  # dp[i][j]

# Output
def out(arr):
    return " ".join(map(str, arr))

# output an array 2 dimensions
def out2dim(arr):
    return '\n'.join("".join(map(str, ans)) for ans in arr)

# solution
def solve(n, m, a):
    x = n-a
    y = m-a
    ans = x+y
    
    return ans

# ----- main() -----
if __name__ == '__main__':
    # https://codeforces.com/problemset/problem/1/A?f0a28=1
    n, m, a = liinp()
    print(solve(n, m, a))