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

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A. 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.

题意：已知有a个偶数b个奇数，判断这些数能不能组成连续正整数数列。

//没有考虑a==b和a=0并且b=0的时候

#include <iostream>

#include<cstdio>

#include<algorithm>

#include<cmath>

using namespace std;

int a,b;

int main()

{

    scanf("%d%d",&a,&b);

    if (abs(a-b)== || a==b && a!= && b!=) printf("YES\n");

     else printf("NO\n");

    return ;

}