D. Little Girl and Maximum XORtime limit per test1 secondmemory limit per test256 megabytesinputstandard inputoutputstandard 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".InputThe single line contains space-separated integers l and r (1 ≤ l ≤ r ≤ 1018).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.OutputIn a single line print a single integer — the maximum value of  for all pairs of integers a, b (l ≤ a ≤ b ≤ r).ExamplesInput1 2Output3Input8 16Output31Input1 1Output0
Input1 2
Output3
['bitmasks', 'dp', 'greedy', 'implementation', 'math', '*1700']