A little girl loves problems on bitwise operations very much. Here's one of them.

You are given two integers *l* and *r*. Let's consider the values of <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/9b77fab607849cb208cd8aab633b62d894fc3358.png" style="max-width: 100.0%;max-height: 100.0%;"/> for all pairs of integers *a* and *b* (*l* ≤ *a* ≤ *b* ≤ *r*). Your task is to find the maximum value among all considered ones.

Expression <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/b364f2e04c665b78b924ec10666327a4ef4635bc.png" style="max-width: 100.0%;max-height: 100.0%;"/> means applying bitwise excluding or operation to integers *x* and *y*. The given operation exists in all modern programming languages, for example, in languages *C*++ and *Java* it is represented as "^", in *Pascal* — as "xor".
The single line contains space-separated integers *l* and *r* (1 ≤ *l* ≤ *r* ≤ 10<sup class="upper-index">18</sup>).

Please, do not use the %lld specifier to read or write 64-bit integers in C++. It is preferred to use the cin, cout streams or the %I64d specifier.
from math import log2
l,r =map(int,input().split())
if l==r:
    print('0')
else:print((1<<int(log2(l^r))+1)-1)
