Little Girl and Maximum XOR
Description:
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 input consists of multiple test cases.
Each test case contains space-separated integers l and r (1 ≤ l ≤ r ≤ 1018).
Output:
In a single line print a single integer — the maximum value of for all pairs of integers a, b (l ≤ a ≤ b ≤ r).
Sample Input:
8 16
Sample Output:
31
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