C语言 问题： Dasha and Stairs

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Dasha and Stairs

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.

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
int main()
{
    int a, b, sum;
    scanf("%d %d", &a, &b);
    if(a > b)  sum = a - b;
    else sum = b - a;
    if(a == 0 && b == 0)  printf("NO\n");//此处很重要，这个特殊情况要注意！！！
    else if(sum <= 1)  printf("YES\n");//当偶数步数和奇数步数次数相差大于1的时候就出错了
    else  printf("NO\n");
    return 0;
}