Dasha and Stairs

题目链接  http://codeforces.com/problemset/problem/761/A

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

题目大意：

输入两个数a,b分别表示偶数个数和技术个数。问是否存在L~R（1 ≤ L ≤ R），是的在L~R这个区间内存在a个偶数，b个奇数。如果存在，输出YES，否则输出NO。

解题思路：

其实只需满足两个条件即可：1=>a-b的绝对值>=0；如果输入的a=b=0，那么显然是不存在的。

代码：

#include<iostream>
#include<cmath>
using namespace std;
int main()
{
int a,b;
while(cin>>a>>b)
{
if(a==0&&b==0)
{
cout<<"NO"<<endl;
continue;
}
if(abs(a-b)>=0&&abs(a-b)<=1)
cout<<"YES"<<endl;
else
cout<<"NO"<<endl;
}
return 0;
}