Maximum XOR
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 a⊕b 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 x⊕y 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».
InputThe single line contains space-separated integers l and r (1 ≤ l ≤ r ≤ 10^18).
OutputIn a single line print a single integer — the maximum value of a⊕b for all pairs of integers a, b (l ≤ a ≤ b ≤ r).
Input:
Output:
1 2Output:
3Input:
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8 16Output:
31Input:
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1 1Output:
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