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

Solution (Python):
import sys
import math
import bisect

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

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())
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):
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())

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

Solution (Python):
a,b,c = map(int,input().split())
dum = b-a
if c == b+dum:
    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):

def ABC_58_A():
    A,B,C = map(int, input().split())
    
    if B == (A+C)/2:
        print('YES')
    else:
        print('NO')

if __name__ == '__main__':

    ABC_58_A()

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 c-b==b-a 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):
def main():
    a,b,c = (int(x) for x in input().split())
    print('YES' if b-a == c-b else 'NO')

if __name__ == '__main__':
    main()

Solution (Python):
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, log2
from itertools import accumulate, permutations, combinations, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
import numpy as np
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()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7
 
a, b, c = MAP()
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):
import sys
sys.setrecursionlimit(10 ** 5 + 10)
def input(): return sys.stdin.readline().strip()

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

Solution (Python):
import sys
def input(): return sys.stdin.readline().strip()

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

Solution (Python):
A, B, C = map(int, input().split())
print(['NO', 'YES'][B - A == C - B])

Solution (Python):
import sys
import itertools
sys.setrecursionlimit(1000000000)
from heapq import heapify,heappop,heappush,heappushpop
import math
import collections
MOD = 10**9 + 7

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

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())
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):
l=list(map(int,input().split()));print('YES'if l.count(sum(l)/3)!=0else'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-b==b-a:
  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):
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 c-b==b-a else print("NO")

Solution (Python):
a,b,c=[int(_) for _ in input().split()]
ans = b-a==c-b
print('YES' if ans 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())
print ("YES") if a-b == b-c 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):
n = input().split()
a = int(n[0])
b = int(n[1])
c = int(n[2])
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=sorted([int(i) for i in input().split()])
if a[1]-a[0]==a[2]-a[1]:
    print("YES")
else:
    print("NO")

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

Solution (Python):
a,b,c=map(int,input().split())
if (b*2==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("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())

A = b - a
B = c - b

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

Solution (Python):
import sys
input = sys.stdin.readline
sys.setrecursionlimit(10**7)
from collections import Counter, deque
from collections import defaultdict
from itertools import combinations, permutations, accumulate, groupby, product
from bisect import bisect_left,bisect_right
from heapq import heapify, heappop, heappush
from math import floor, ceil
from operator import itemgetter
def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))
def LI2(): return [int(input()) for i in range(n)]
def MXI(): return [[LI()]for i in range(n)]
inf = 10**17
mod = 10**9 + 7

a,b,c=MI()
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):

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


if '__main__' == __name__:
    resolve()

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())
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 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())

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

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

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):
x, y, z = map(int,input().split())

print("YES") if 2*y == x+z 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())

A = b - a
B = c - b
if A==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 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())
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())

ba = b-a
cb =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())

print('YES' if c-b==b-a 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())

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 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())

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

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())
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):
icase=0    
if icase==0:
    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())

d = b - c
e = a - 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 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())
ans = 'YES' if b-a == c-b else 'NO'
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 = [int(x) for x in input().split()]
print('YES') if b - a == c - b 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())
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 a - b == b - c else '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())

BA = B-A
CB = C-B

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

Solution (Python):
import io
import sys

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

Solution (Python):
l = list(map(int, input().split()))
if (l[2]-l[1]) == (l[1]-l[0]):
  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())
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 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 a+c == b+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())
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())
print('YES' if b-a==c-b else'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());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 = [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):
import sys

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

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

if __name__ ==  '__main__':
    main()

Solution (Python):

a, b, c = [int(x) for x in 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())
r = 'YES' if b - a == c - b else 'NO'
print(r)

Solution (Python):
def ii():return int(input())
def iim():return map(int,input().split())
def iil():return list(map(int,input().split()))

a,b,c = iim()

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
import copy
import math
import bisect
import pprint
import bisect
from functools import reduce
from copy import deepcopy
from collections import deque

if __name__ == '__main__':
    a = [int(i) for i in input().split()]

    if a[1] -a[0] == a[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())
result  = 'YES' if (b - a) == (c - b) else 'NO'
print(result)

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, raw_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());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):


import sys
 
stdin = sys.stdin
inf = 1 << 60
mod = 1000000007
 
ni      = lambda: int(ns())
nin     = lambda y: [ni() for _ in range(y)]
na      = lambda: list(map(int, stdin.readline().split()))
nan     = lambda y: [na() for _ in range(y)]
nf      = lambda: float(ns())
nfn     = lambda y: [nf() for _ in range(y)]
nfa     = lambda: list(map(float, stdin.readline().split()))
nfan    = lambda y: [nfa() for _ in range(y)]
ns      = lambda: stdin.readline().rstrip()
nsn     = lambda y: [ns() for _ in range(y)]
ncl     = lambda y: [list(ns()) for _ in range(y)]
nas     = lambda: stdin.readline().split()

a, b, c = na()

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())
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())
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())

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

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

Solution (Python):
import math

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())
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 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())
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')
  exit()
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())

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 c - b == b - a:
    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=list(N)
if (int(N[1])-int(N[0]))==(int(N[2])-int(N[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 = list(map(int, input().split()))

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

Solution (Python):
a,b,c = map(int,input().split())
k1 = b-a
k2 = c-b

if k1==k2:
  print("YES")
else:
  print("NO")

Solution (Python):
n = list(map(int, input().split()))
s=n[0]+n[2]
s1=2*n[1]
if(s1==s):
    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+c)==b*2):
 print('YES')
else:
 print('NO')

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

a=int(a)
b=int(b)
c=int(c)

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):
def main():
    a, b, c = (int(i) for i in input().split())
    if b - a == c - b:
        print("YES")
    else:
        print("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):
import sys, re, os
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
def input(): return sys.stdin.readline().strip()
def STR(): return input()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def S_MAP(): return map(str, input().split())
def LIST(): return list(map(int, input().split()))
def S_LIST(): return list(map(str, input().split()))
sys.setrecursionlimit(10 ** 9)
inf = sys.maxsize
mod = 10 ** 9 + 7

a, b, c = MAP()
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=sorted(list(map(int,input().split())))
if a[1]-a[0]==a[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())
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(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())
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):
import sys
import os


def main():
    if os.getenv("LOCAL"):
        sys.stdin = open("input.txt", "r")

    a, b, c = list(map(int, sys.stdin.readline().split()))
    print('YES' if b - a == c - b else 'NO')


if __name__ == '__main__':
    main()

Solution (Python):
import sys
input = sys.stdin.readline

def I(): return int(input())
def MI(): return map(int, input().split())
def LI(): return list(map(int, input().split()))

def main():
    mod=10**9+7
    a,b,c=MI()
    f=0
    if b-a==c-b:
        f=1
        
    if f==1:
        print("YES")
    else:
        print("NO")

main()

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