Dasha and Stairs

Dasha and Stairs

time limit per test

2 seconds

memory limit per test

256 megabytes

input

standard input

output

standard output

On her way to programming school tiger Dasha faced her first test — a huge staircase!

The steps were numbered from one to infinity. As we know, tigers are very fond of all striped things, it is possible that it has something to do with their color. So on some interval of her way she calculated two values — the number of steps with even and odd numbers.

You need to check whether there is an interval of steps from the l-th to the r-th (1 ≤ l ≤ r), for which values that Dasha has found are correct.

Input

In the only line you are given two integers a, b (0 ≤ a, b ≤ 100) — the number of even and odd steps, accordingly.

Output

In the only line print "YES", if the interval of steps described above exists, and "NO" otherwise.

Examples

input

2 3

output

YES

input

3 1

output

NO

Note

In the first example one of suitable intervals is from 1 to 5. The interval contains two even steps — 2 and 4, and three odd: 1, 3 and 5.

解题说明：此题是一道模拟题，给定奇数偶数个数,很显然，奇偶数相差必须为不超过1才行。

一直不对，结果发现最后才知道ab不能为零，mmp

    #include<stdio.h>  
    #include<string.h>  
    #include<math.h>  
      
    int main()  
    {  
        int a,b;  
        scanf("%d %d",&a,&b);  
        if(abs(b-a)<=1&&(b!=0||a!=0))  
        {  
            printf("YES\n");  
        }  
        else  
        {  
            printf("NO\n");  
        }  
        return 0;  
    }