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 (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())

print("YES" if a-b==b-c else "NO")

Solution (Python):
a,b,c=map(int,input().split())
print('YES' if b-a == c-b else 'NO')

Solution (Python):
A,B,C = map(int,input().split())

if 2*B == A + C :
  print('YES')
  
else:
  print('NO')

Solution (Python):
a,b,c=map(int,input().split())
print("YES"if b-a==c-b else "NO")

Solution (Python):
a,b,c = map(int,input().split())
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int, input().split())
if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = list(map(int, input().split()))
print("YES") if b - a == c - b else print("NO")

Solution (Python):

import sys


YES = "YES"  
NO = "NO"  


def solve(a: int, b: int, c: int):
    print(YES if b - a == c - b else NO)


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    a = int(next(tokens))  
    b = int(next(tokens))  
    c = int(next(tokens))  
    solve(a, b, c)


if __name__ == '__main__':
    main()

Solution (Python):
a, b, c = map(int, input().split())

if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
  print("YES")
else:
  print("NO")

Solution (Python):
A,B,C=map(int,input().split())
if B-A==C-B:
	print("YES")
else:
	print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):

a,b,c = map(int, input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = (int(x) for x in input().split())

if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print('YES')
else:
  print('NO')

Solution (Python):

a, b, c = map(int, input().split())

if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):

a,b,c=map(int,input().split())
print('YES' if b-a==c-b else 'NO')

Solution (Python):
a = list(map(int, input().split()))
a.sort()
if abs(a[1]-a[0]) == abs(a[2]-a[1]):
	print ("YES")
else:
	print ("NO")

Solution (Python):
a, b, c = map(int, input().split())

print('YES' if b - a == c - b else 'NO')

Solution (Python):
a,b,c = map(int,input().split())
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())

if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())
print("YES" if b - a == c - b else "NO")

Solution (Python):
a,b,c=map(int,input().split())
print("YES") if b-a==c-b else print("NO")

Solution (Python):
[a,b,c]=list(map(int,input().split()))
ans="NO"
if b-a==c-b:
    ans="YES"
print(ans)

Solution (Python):
a,b,c=map(int,input().split())
print('YNEOS'[b-a!=c-b::2])

Solution (Python):
import sys
import bisect
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
a,b,c = map(int,readline().split())

if  a <= b <= c or a >= b >= c:
    if abs(a-b)==abs(b-c):
        print("YES")
        exit()
print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print("YES" if b - a == c - b else "NO")

Solution (Python):
a,b,c=map(int,input().split())

if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
def main():
    a, b, c = map(int, input().split())
    print("YES" if b - a == c - b else "NO")


if __name__ == '__main__':
    main()

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):



a,b,c = list(map(int, input().rstrip().split()))

if (b-a) == (c-b):
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a != c - b:
    print('NO')
else:
    print('YES')

Solution (Python):
a,b,c = map(int, input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c = map(int,input().split())

if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a, b, c = [int(_) for _ in input().split()]
if a + c == 2 * b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if (b - a) == (c - b):
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a,b,c= map(int,input().split())
if a-b == b-c:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int,input().split())
print("YES" if b-a == c-b else "NO")

Solution (Python):

a,b,c = map(int,input().split())
print("YES" if b-a == c-b else "NO")

Solution (Python):
a,b,c = map(int,input().split())

if(b-a == c-b):
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c - b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = list(map(int, input().split()))

if b - a == c - b:
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c = map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b, c = map(int, input().split())
if a + c == 2*b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c=list(map(int,input().split()))
if (b-a)==(c-b):
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int,input().split())

if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):

import sys

YES = "YES"  
NO = "NO"  


def solve(a: int, b: int, c: int):
    print("YES" if b - a == c - b else "NO")
    return



def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    a = int(next(tokens))  
    b = int(next(tokens))  
    c = int(next(tokens))  
    solve(a, b, c)

if __name__ == '__main__':
    main()

Solution (Python):
a,b,c = map(int,input().split())
print("YES" if b-a == c-b else "NO")

Solution (Python):

a,b,c = map(int,input().split())
if a + c == 2 * b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int, input().split())
print('YES' if b-a == c-b else 'NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int, input().split())
print('YES' if (a+c)/2 == b else 'NO')

Solution (Python):
a,b,c = map(int,input().split())
if b-a == c-b :
  print("YES")
else :
  print("NO")

Solution (Python):
a,b,c = [int(x) for x in input().rstrip().split()]
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c, = map(int,input().split())
print("YES" if b * 2 - (a + c) == 0 else "NO")

Solution (Python):
a, b, c, = map(int,input().split())
if b - a == c - b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = map(int,input().split())
print('YNEOS'[a-b!=b-c::2])

Solution (Python):
a, b, c= map(int, input().split())
print("YES" if a - b == b - c else "NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
A, B, C = map(int,input().split())

if B - A == C - B:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
print('YES' if b-a==c-b else 'NO')

Solution (Python):
x = sorted(list(map(int,input().split())))

if x[1]-x[0] == x[2]-x[1]:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int, input().split())
if 2*b==a+c: print('YES')
else: print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split());print('YNEOS'[a-b!=b-c::2])

Solution (Python):
a,b,c=map(int,input().split())
print('YNEOS'[a-b != b-c::2])

Solution (Python):


a, b, c = map(int, input().split())
if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
d=b-a
e=c-b
if d==e:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int,input().split())
if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int,input().split())

if (2*b-a-c)==0:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = list(map(int, input().split()))
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int,input().split())
print(["NO","YES"][b-a==c-b])

Solution (Python):

a, b, c = map(int, input().split())


if b-a == c-b :
    print("YES")
else :
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:print("YES")
else:print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
  print("YES")
else:
  print("NO")

Solution (Python):
a = list(map(int,input().split()))
if a[1] - a[0] == a[2] - a[1]:
  print("YES")
else:
  print("NO")

Solution (Python):
x,y,z = map(int,input().split())
if (y-x)==(z-y):
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print('YES' if (b - a) == (c - b) else 'NO')

Solution (Python):
x,y,z = map(int,input().split())
if (y-x)==(z-y):
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = [int(i) for i in input().split()]
print("YES" if b-a == c-b else "NO")

Solution (Python):
x,y,z = map(int,input().split())
if (y-x)==(z-y):
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c -b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = [int(i) for i in input().split()]
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
print("YNEOS"[(b-a!=c-b)::2])

Solution (Python):
def ntukusi(a,b,c):
    return "YES" if (b - a) == (c - b) else "NO"

def main():
    a , b , c = map(int, input().split())
    print(ntukusi(a , b , c))

if __name__ == '__main__':
    main()

Solution (Python):
A,B,C=map(int,input().split())
if (B-A)==(C-B):
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = list(map(int,input().split()))
if b-a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import permutations, combinations, product, accumulate
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from fractions import gcd
from bisect import bisect

def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

a, b, c = MAP()

if b-a == c-b:
	print("YES")
else:
	print("NO")

Solution (Python):
a, b, c = tuple(map(int, input().split()))

diff_ab = b - a
diff_cb = c - b
if diff_ab == diff_cb:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b: print("YES")
else: print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print("YES" if c - b == b - a else "NO")

Solution (Python):




def main():
    A, B, C = map(int, input().split())
    print('YES'if B - A == C - B else 'NO')


if __name__ == "__main__":
    main()

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = map(int, input().split())
if (b - a) == (c - b):
    print("YES")
else:
    print("NO")

Solution (Python):
"""
author : halo2halo
date : 30, Jan, 2020
"""

import sys
import itertools



read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

a,b,c = map(int, readline().decode('utf8').split())

print('YES' if 2 * b == a + c else 'NO')

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int, input().split())
if b-a==c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int,input().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print('YES' if b-a == c-b else 'NO')

Solution (Python):
a, b, c = map(int, input().split())
print("YNEOS"[b-a!=c-b::2])

Solution (Python):
a,b,c = map(int, input().split())
print('YES' if b-a == c-b else 'NO')

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = map(int,input().split())
if a+c == 2*b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
import sys

sys.setrecursionlimit(10 ** 6)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def SI(): return sys.stdin.readline()[:-1]

def main():
    a,b,c=MI()
    if b-a==c-b:print("YES")
    else:print("NO")
main()

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = map(int,input().split())

if a-b == b-c:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
import sys
input = sys.stdin.readline
a,b,c = [int(i) for i in input().split()]
if b - a == c - b :
    print("YES")
else :
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if a + c == 2 * b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a, b, c = list(map(int, input().split()))

if b - a == c - b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = map(int,input().split())
if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = map(int,input().split())
print("YES" if b-a == c-b else "NO")

Solution (Python):
a,b,c = map(int,input().split())

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())
print('YES' if b - a == c - b else 'NO')

Solution (Python):
a,b,c=list(map(int,input().split()))
if b-a==c-b:
  print ('YES')
else:
  print ('NO')

Solution (Python):
a, b, c = map(int, input().split())
if (b - a) == (c - b):
    print("YES")
else:
    print("NO")

Solution (Python):
A, B, C = map(int, input().split())

if B-A == C-B:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int, input().split())
print("YES" if b - a == c - b else "NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
import sys
input = sys.stdin.readline
a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b,c = map(int, input().split())

if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b :
	print("YES")
else:
	print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())
if a + c == b * 2:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = map(int, input().split())
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
n = input().split()

n_i = [int(s) for s in n]

a, b, c = n_i

if (b-a == c-b):
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int, input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int, input().split())
if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int,input().split())

if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int,input().split())

if b-a==c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:print('YES')
else:print('NO')

Solution (Python):
a, b, c = map(int, input().split())
x = b - a
y = c - b
if x == y:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = (int(i) for i in input().split())
if b-a == c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = [int(s) for s in input().split()]

print(["NO", "YES"][a - b == b - c])

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=list(map(int,input().split()))
if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
import sys
input = sys.stdin.readline
a, b, c = [int(x) for x in input().split()]
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(lambda x: int(x), input().split())
if b - a == c - b:
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = map(int, input().split())
print('YES' if b-a==c-b else 'NO')

Solution (Python):
a, b, c = map(int,(input().split()))
ans = "NO"
if a-b == b-c or b-a == c-b:
  ans = "YES"
print(ans)

Solution (Python):
a,b,c = map(int,input().split())
if b - a == c - b :
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
print('YES' if b-a == c-b else 'NO')

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
print("YES" if (b-a)==(c-b) else "NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if (b - a == c - b):
   print('YES')
else:
   print('NO')

Solution (Python):
a, b, c = map(int, input().split())

print("YES" if b-a==c-b else "NO")

Solution (Python):
a,b,c=map(int,input().split())

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print("YES" if b-a == c-b else "NO")

Solution (Python):
a,b,c = map(int,input().split()) 
if b-a == c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
import math
import queue
import bisect
import heapq
import time
import itertools

mod = int(1e9+7)

def swap(a,b):
    return (b,a)

def gcd(a,b): 
    if (a<b):
        a,b = swap(a,b)
    if (b==0):
        return a
    else:
        return gcd(b,a%b)

def lcm(a,b): 
    return a/gcd(a,b)*b

def divisors(a): 
    divisors = []
    for i in range(1,int(a**0.5)+1):
        if a%i==0:
            divisors.append(i)
            if i!=a//i:
                divisors.append(a//i)
    return divisors

def is_prime(a): 
    if a<2:
        return False
    elif a==2:
        return True
    elif a%2==0:
        return False
    sqrt_num = int(a**0.5)
    for i in range(3,sqrt_num+1,2):
        if a%i==0:
            return False
    return True

def prime_num(a): 
    pn = [2]
    for i in range(3,int(a**0.5),2):
        prime = True
        for j in pn:
            if i%j==0:
                prime = False
                break
        if prime:
            pn.append(i)
    return pn

def prime_fact(a): 
    sqrt = math.sqrt(a)
    res = []
    i = 2
    if is_prime(a):
        res.append(a)
    else:
        while a!=1:
            while a%i==0:
                res.append(i)
                a //= i
            i += 1
    return res

def main():
    a,b,c = map(int,input().split())
    if b - a == c - b:
        print('YES')
    else:
        print("NO")
    return

if __name__=='__main__':
    main()

Solution (Python):
a,b,c=map(int,input().split())
print('YES' if b-a==c-b else 'NO')

Solution (Python):
a,b,c = map(int,input().split())
if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = map(int,input().split())
print('YES' if b-a==c-b else 'NO')

Solution (Python):
a,b,c = map(int, input().split())
if (b - a == c - b):
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())
if c-b == b-a:
    ans = 'YES'
else:
    ans = 'NO'

print(ans)

Solution (Python):
a,b,c = map(int, input().split())
print("YES" if b-a == c-b else "NO")

Solution (Python):
a, b, c = map(int, input().split())
if(b - a == c - b):
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
	print("YES")
else:
	print("NO")

Solution (Python):
a, b, c = list(map(int, input().split()))
print('YES' if b - a == c - b else 'NO')

Solution (Python):
a, b, c = map(int, input().split())

if (b - a) == (c - b):
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = list(map(int, input().split()))
print('YES' if b-a==c-b else 'NO')

Solution (Python):
import sys
MAX_INT = int(10e12)
MIN_INT = -MAX_INT
mod = 1000000007
sys.setrecursionlimit(1000000)
def IL(): return list(map(int,input().split()))
def SL(): return input().split()
def I(): return int(sys.stdin.readline())
def S(): return input()

a,b,c = IL()
if b*2 == a + c:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = map(int,input().split())
print('YES') if b-a == c-b else print('NO')

Solution (Python):
a, b, c = map(int, input().split())
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if (b-a)==(c-b):
    print("YES")
else:
    print("NO")

Solution (Python):
import math

a, b, c = map(int, input().split())
print("YES" if b - a == c - b else "NO")

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
  print('YES')
else:
  print('NO')

Solution (Python):
a, b, c = map(int, input().split())

print('YES' if b-a == c-b else 'NO')

Solution (Python):
a,b,c = map(int,input().split())
if c + a - b*2 == 0:
  print("YES")
else:
  print("NO")

Solution (Python):

import sys, math, itertools, collections, bisect
input = lambda: sys.stdin.buffer.readline().rstrip().decode('utf-8')
inf = float('inf')
ans = 0 ;count = 0 ;pro = 1

a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):

import sys, math, itertools, collections, bisect
input = lambda: sys.stdin.buffer.readline().rstrip().decode('utf-8')
inf = float('inf')
ans = 0 ;count = 0 ;pro = 1

a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b, c = map(int, input().split())
if (b - a) == (c - b):
    print('YES')
else:
    print('NO')

Solution (Python):
import sys

a,b,c = map(int, sys.stdin.readline().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a,b,c = list(map(int,input().split()))
if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
import sys

a, b, c = map(int, sys.stdin.readline().split())

def main():
    return 'YES' if b - a == c - b else 'NO'

if __name__ == '__main__':
    ans = main()
    print(ans)

Solution (Python):
a, b, c = list(map(int, input().split()))
if b - a == c - b :
  print("YES")
else :
  print("NO")

Solution (Python):

a,b,c = map(int, input().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a = input().split()
if int(a[1]) - int(a[0]) == int(a[2]) - int(a[1]):
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c = [int(i) for i in input().split()]
 
if (b-a)==(c-b):
	print('YES')
else:
	print('NO')

Solution (Python):
a,b,c=map(int,input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b, c= map(int, open(0).read().split())
if b-a == c-b:
	print('YES')
else:
	print('NO')

Solution (Python):
a, b, c= map(int, open(0).read().split())
if b-a == c-b:
	print('YES')
else:
	print('NO')

Solution (Python):
a, b, c = map( int, input().split() )
if b - a == c - b : 
   print( "YES" )
else : 
   print( "NO" )

Solution (Python):
a, b, c = map(int,input().split())
if c - b == b - a:
	print("YES")
else:
	print("NO")

Solution (Python):
a,b,c=map(int,input().split())
k=(b-a)
l=c-b
if k==l:
  print("YES")
else:
  print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if a-b==b-c:
  print("YES")
else:
  print("NO")

Solution (Python):
a, b, c = map(int, input().split())
b_a = b - a
c_b = c - b

if b_a == c_b:
	print("YES")
else:
	print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print('YES' if b-a == c-b else 'NO')

Solution (Python):
a, b, c = map(int, input().split())
if (b - a == c - b):
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split(" "))

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
A=list(map(int, input().split()))
A.sort()
if A[0]+A[2]==2*A[1]:
  print('YES')
else:
  print('NO')

Solution (Python):
a,b,c=map(int,input().split())
if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
print('YES') if b - a == c - b else print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c=map(int, input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split(" "))

print("YES" if b - a == c - b else "NO")

Solution (Python):
a, b, c = map(int, input().split())
print('YES' if (max(a, b, c) + min(a, b, c)) / 2 == (a + b + c) / 3 else 'NO')

Solution (Python):
a, b, c = (int(i) for i in input().split())

if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c = map(int, input().split())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int, input().split())

if a-b == b-c:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=list(map(int,input().split(" ")))
if (b-a)==(c-b):
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int,input().split());print(" YNEOS"[b-a==c-b::2])

Solution (Python):
a, b, c = map(int, input().split())

if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c=map(int, input().split())
print("YES" if b-a==c-b else "NO")

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):
a, b, c=map(int, input().split())
if b-a==c-b:
    print("YES")
else:
    print("NO")

Solution (Python):
from sys import stdin

a,b,c = [int(x) for x in stdin.readline().rstrip().split()]

if b-a == c-b:
    print("YES")
else:
    print("NO")

Solution (Python):

import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**6)

a, b, c = map(int, input().split())
print('YNEOS'[b-a != c-b::2])

Solution (Python):
a,b,c = map(int,input().split())

if b-a == c-b:
  print("YES")
else:
  print("NO")

Solution (Python):
a,b,c = map(int,input().split())
if b-a == c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
def main():
    a, b, c = map(int, input().split())
    if b - a == c - b:
        print('YES')
    else:
        print('NO')


main()

Solution (Python):
a, b, c = map(int, input().split())

if b - a == c - b:
    print('YES')
else:
    print('NO')

Solution (Python):
a, b, c = map(int,input().split())
if b-a == c-b:
	print ("YES")
else:
	print ("NO")

Solution (Python):
a, b, c = list(map(int, input().split()))
if b - a == c - b:
    print("YES")
else:
    print("NO")

Solution (Python):


a,b,c=list(map(int,input().split(" ")))

if (b-a)==(c-b): 
    print("YES")
else: 
    print("NO")