Codeforces Round #394(Div. 2)A.Dasha and Stairs【水题】

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

$\text{[math]}$

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.

题目大意：

问你是否包含一段数字，其中有a个偶数，b个奇数。

思路：

数字是奇偶排列的，那么如果abs（a-b）<=1就是可能的情况。

注意一段数字不能为空，所以a==0&&b==0的时候特判一下输出NO.

Ac代码：

#include<stdio.h>
#include<string.h>
using namespace std;
#define ll __int64
#define mod 1000000007
int abs(int a)
{
    if(a<0)return -a;
    else return a;
}
int main()
{
    int a,b;
    while(~scanf("%d%d",&a,&b))
    {
        if(a==0&&b==0)
        {
            printf("NO\n");
            continue;
        }
        if(abs(a-b)<=1)
        {
            printf("YES\n");
        }
        else printf("NO\n");
    }
}