Dasha and Stairs
题目描述
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.
In the only line you are given two integers a, b (0≤a,b≤100) − the number of even and odd steps, accordingly.
In the only line print "YES", if the interval of steps described above exists, and "NO" otherwise.
2 3
YES
3 1
NO
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.
题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 376 题。保留原作者与原赛事署名。