Problem:
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.

Solution in Java (OpenJDK 11.0.6) (judge verdict: Wrong Answer)


import java.math.BigInteger;
import java.util.*;
public class Main {





public static void main(String[] args)
{
	Scanner sc=new Scanner(System.in);
			int a=sc.nextInt();
			int b=sc.nextInt();
			int c=sc.nextInt();
			if(b==(a+c)/2) {
				System.out.println("YES");
			}else {
				System.out.println("NO");
			}
}
}

class pair{
	int x,y;
	pair(int x,int y){
		this.x=x;
		this.y=y;
	}
}