H. The Magic of Squares
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Two students — Yerlan and Daulet — are passionate about mathematics and enjoy experimenting with numbers. One day, Yerlan chose a number $$$a$$$, and Daulet chose a number $$$b$$$. Together, they decided to compute the expression $$$a^2 - b^2$$$ and find out whether the result can be a prime number.

Recall that a prime number is an integer greater than 1 that is divisible only by 1 and itself. Help the students determine whether their result is a prime number.

Input

The first line contains two integers $$$a$$$ and $$$b$$$ $$$(1 \le b \lt a \le 10^{12})$$$ — the numbers chosen by Yerlan and Daulet, respectively.

Output

Print YES (without quotes) if the value of the expression is a prime number, otherwise print NO.

You may print each letter in any case (uppercase or lowercase).

Example
Input
2 1
Output
YES