Problem Statement

Let f(A, B) be the exclusive OR of A, A+1, ..., B. Find f(A, B).

The bitwise exclusive OR of integers c_1, c_2, ..., c_n (let us call it y) is defined as follows:

• When y is written in base two, the digit in the 2^k's place (k \geq 0) is 1 if, the number of integers among c_1, c_2, ...c_m whose binary representations have 1 in the 2^k's place, is odd, and 0 if that count is even.

For example, the exclusive OR of 3 and 5 is 6. (When written in base two: the exclusive OR of 011 and 101 is 110.)