100580: [AtCoder]ABC058 A - ι⊥l

Memory Limit:256 MB Time Limit:2 S
Judge Style:Text Compare Creator:
Submit:0 Solved:0

Description

Score : $100$ points

Problem Statement

Three poles stand evenly spaced along a line. Their heights are $a$, $b$ and $c$ meters, from left to right. We will call the arrangement of the poles beautiful if the tops of the poles lie on the same line, that is, $b-a = c-b$.

Determine whether the arrangement of the poles is beautiful.

Constraints

  • $1 \leq a,b,c \leq 100$
  • $a$, $b$ and $c$ are integers.

Input

Input is given from Standard Input in the following format:

$a$ $b$ $c$

Output

Print YES if the arrangement of the poles is beautiful; print NO otherwise.


Sample Input 1

2 4 6

Sample Output 1

YES

Since $4-2 = 6-4$, this arrangement of poles is beautiful.


Sample Input 2

2 5 6

Sample Output 2

NO

Since $5-2 \neq 6-5$, this arrangement of poles is not beautiful.


Sample Input 3

3 2 1

Sample Output 3

YES

Since $1-2 = 2-3$, this arrangement of poles is beautiful.

Input

题意翻译

三个竹竿沿着一条直线间隔相同距离直立。它们的高度从左到右分别是A、B、C米。如果三个杆子的顶部位于同一条直线上,即B-A=C-B,,则我们称之为极点的排列。 请确定极点的排列是否美观。 大意:给出A,B,C三个数,用空格隔开。判断B-A=C-B是否成立,若成立,则输出YES,否则输出NO。 A,B,C均为正整数,1<=A,B,C<=100 由 @找寻 提供翻译

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