Problem Statement

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

What is exclusive OR? 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.)

Constraints

• All values in input are integers.
• $0 \leq A \leq B \leq 10^{12}$

Input

Input is given from Standard Input in the following format:

A B

Output

Compute $f(A, B)$ and print it.