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D. Little Girl and Maximum XOR

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputA 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 С++. 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*).

Examples

Input

1 2

Output

3

Input

8 16

Output

31

Input

1 1

Output

0

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