Problem Statement

You are given integers $L,R$ ($L < R$).

Snuke is looking for a pair of integers $(x,y)$ that satisfy both of the conditions below.

• $L \leq x < y \leq R$
• $\gcd(x,y)=1$

Find the maximum possible value of $(y-x)$ in a pair that satisfies the conditions. It can be proved that at least one such pair exists under the Constraints.

Constraints

• $1 \leq L < R \leq 10^{18}$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

L R

Output

Print the answer.