CF761A.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.

在去编程学校的路上，老虎达莎遇到了她的第一次测试——一段巨大的楼梯！

台阶编号从 1 开始，一直延伸至无穷。众所周知，老虎非常喜爱所有条纹状的东西，这或许与它们的毛色有关。因此，在她所走的一段连续台阶上，她计算了两个值：其中编号为偶数的台阶数量与编号为奇数的台阶数量。

你需要判断：是否存在一个从第 $l$ 级到第 $r$ 级的台阶区间（满足 $1 \le l \le r$），使得达莎所计算出的这两个值是正确的。

In the only line you are given two integers a, b (0 ≤ a, b ≤ 100) — the number of even and odd steps, accordingly.

在唯一的一行中，给你两个整数 $a$、$b$（$0 ≤ a, b ≤ 100$），分别表示偶数步数和奇数步数。

In the only line print "YES", if the interval of steps described above exists, and "NO" otherwise.

在唯一的一行中输出 "YES"，如果上述描述的步长区间存在；否则输出 "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.

在第一个例子中，一个合适的区间是从 1 到 5。该区间包含两个偶数——2 和 4，以及三个奇数：1、3 和 5。