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):











import sys
sys.setrecursionlimit(10**6)
input=sys.stdin.readline
from math import floor,ceil,sqrt,factorial,log 
from heapq import heappop, heappush, heappushpop
from collections import Counter,defaultdict,deque
from itertools import accumulate,permutations,combinations,product,combinations_with_replacement
from bisect import bisect_left,bisect_right
from copy import deepcopy
inf=float('inf')
mod = 10**9+7
def pprint(*A): 
    for a in A:     print(*a,sep='\n')
def INT_(n): return int(n)-1
def MI(): return map(int,input().split())
def MF(): return map(float, input().split())
def MI_(): return map(INT_,input().split())
def LI(): return list(MI())
def LI_(): return [int(x) - 1 for x in input().split()]
def LF(): return list(MF())
def LIN(n:int): return [I() for _ in range(n)]
def LLIN(n: int): return [LI() for _ in range(n)]
def LLIN_(n: int): return [LI_() for _ in range(n)]
def LLI(): return [list(map(int, l.split() )) for l in input()]
def I(): return int(input())
def F(): return float(input())
def ST(): return input().replace('\n', '')
def main():
    a,b,c = MI()
    print("YNEOS"[not(b-a==c-b)::2])
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())

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())
if((b-a)==(c-b)):
  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):

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

Solution (Python):

import math


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):

si = lambda: input()
ni = lambda: int(input())
nm = lambda: map(int, input().split())
nl = lambda: list(map(int, input().split()))
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())
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(["NO","YES"][b-a==c-b])

Solution (Python):
def examA():
    a, b, c = LI()
    da = b-a
    db = c-b
    if da==db:
        ans="YES"
    else:
        ans="NO"
    print(ans)


import sys
import copy
import bisect
from collections import Counter,defaultdict,deque
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))
def LS(): return sys.stdin.readline().split()
def S(): return sys.stdin.readline().strip()
mod = 10**9 + 7
inf = float('inf')

examA()

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,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 :
	ans = 'YES'
else:
	ans = '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 =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 (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())
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(s) for s 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())
print('YNEOS'[not((b-a)==(c-b))::2])

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

Solution (Python):
f=lambda x:x[0]-2*x[1]+x[2]==0
print('YES' if f(list(map(int,input().split()))) 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 - 2*b + 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 = (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 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 a + c == b * 2:
    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())
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())
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 = input().split()

if (int(b) - int(a)) == (int(c) - int(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())
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())
print('YES' if a+c==2*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())
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())
print("YNEOS"[(c-b!=b-a)::2])

Solution (Python):
A= list(map(int,input().split()))
a=A[0]
b=A[1]
c=A[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, 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())

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

Solution (Python):
a, b, c = tuple(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("NO" if 2*b-a-c else "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 = 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('YNEOS'[b-a!=c-b::2])

Solution (Python):

a, b, c = map(int, open(0).read().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):
def slove():
    import sys
    input = sys.stdin.readline
    a, b, c = list(map(int, input().rstrip('\n').split()))
    print("YES" if b - a == c - b else "NO")


if __name__ == '__main__':
    slove()

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

input = sys.stdin.readline


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):
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 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())
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 ba == cb:
  print("YES")
else:
  print("NO")

Solution (Python):
INT = lambda: int(input())
INTM = lambda: map(int,input().split())
STRM = lambda: map(str,input().split())
STR = lambda: str(input())
LIST = lambda: list(map(int,input().split()))
def do():
    a,b,c = INTM()
    if (a+c)/2 == b:
        print('YES')
    else:
        print('NO')
if __name__ == '__main__':
    do()

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(s) for s 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())
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())
gap1 =a-b
gap2=b-c
if gap1==gap2:
    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 = [int(n) for n in input().split()]
print('YES' if B * 2 == 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())
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 A-B == B-C else "NO")

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

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

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


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

Solution (Python):
x=list(input().split())
x1=int(x[0])
x2=int(x[1])
x3=int(x[2])
if (x2-x1)==(x3-x2):
  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())
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 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 "NO")

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 = (int(x) for x in input().split())

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

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

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

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

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

Solution (Python):

s=input().split()
a=int(s[0])
b=int(s[1])
c=int(s[2])

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())
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 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 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):
import sys

if sys.platform =='ios':
    sys.stdin=open('input_file.txt')
    
    
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):
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 collections
import copy
def input(): return sys.stdin.readline().strip()
A,B,C= map(int,input().split())
if (B-A) == (C-B):
    print("YES")
else:
    print("NO")

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

Solution (Python):
a = [int(_) for _ in input().split()]
if all(1 <= i <= 100 for i in a):
    print('YES' if a[1] - a[0] == a[2] - a[1] else 'NO')
else:
    print('hoge!')

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
import copy
import  math
from _bisect import *
from collections import *
from operator import itemgetter
from math import factorial
"""
from fractions import gcd
def lcm(x, y):
    return (x * y) // gcd(x, y)
"""
stdin = sys.stdin
ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline()

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

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

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

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

Solution (Python):
a,b,c = map(int,input().split())
print("YES") if a+c==2*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());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):
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 = (int(i) for i 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 = list(map(int,input().split()))

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

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

ns = lambda: stdin.readline().rstrip()
ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
s = lambda h: [list(map(int, stdin.readline().split())) for i in range(h)]

a, b, c = na()

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().strip().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 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 c - b == b - a else print("NO")

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

Solution (Python):
nums = list(map(int,input().split()))
if nums[1]-nums[0] == nums[2]-nums[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())
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())
a, b, c = sorted([a, b, c])
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())
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("YNEOS"[a+c!=2*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())
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()))
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 c - b == b - a:
    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 b-a==c-b else 'NO')

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


if __name__ == "__main__":
    test()

Solution (Python):


import numpy as np

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

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

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

Solution (Python):

import sys
INF = float("inf")


def yes():
    print("YES")  


def no():
    print("NO")  


def solve(a: int, b: int, c: int):
    if b-a == c-b:
        yes()
    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())
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 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())
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")