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 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 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".

Input

The single line contains space-separated integers $*l*$ and $*r*$ ($1 ≤ *l* ≤ *r* ≤ 10^{18}$).

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.

Output

In a single line print a single integer — the maximum value of for all pairs of integers $*a*$, $*b*$ $(*l* ≤ *a* ≤ *b* ≤ *r*)$.