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

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

Solution (Python):
(a, b, c) = (int(tok) for tok in 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 - 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())

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

Solution (Python):

import sys
import copy
import collections
from bisect import bisect_left
from bisect import bisect_right
from collections import defaultdict
from heapq import heappop, heappush, heapify
import math
import itertools
import random
 




 
INF = float('inf')
def inputInt(): return int(input())
def inputMap(): return map(int, input().split())
def inputList(): return list(map(int, input().split()))
 
def main():
    a,b,c = inputMap()
    
    if b-a == c-b:
        print("YES")
    else:
        print("NO")
    
    
if __name__ == "__main__":
	main()

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

Solution (Python):
import sys
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):
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 = 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())
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):


a, b, c = map(int, 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 - 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())
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 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());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 = list(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):
num = input().split()
if int(num[1])-int(num[0])==int(num[2])-int(num[1]): print('YES')
else: print('NO')

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

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


main()

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

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

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

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

Solution (Python):
a,b,c=map(int,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 or a-b == b-c:print("YES")
else:print("NO")

Solution (Python):
a, b, c = map(int, input().split())
ans = 'NO'
if 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):
from collections import defaultdict, Counter

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())

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):
a, b, 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'[a+c!=b*2::2])

Solution (Python):

from collections import defaultdict
from collections import deque
from heapq import heappush, heappop
import sys
import math
import bisect
import random
import itertools
sys.setrecursionlimit(10**5)
stdin = sys.stdin
bisect_left = bisect.bisect_left
bisect_right = bisect.bisect_right
def LI(): return list(map(int, stdin.readline().split()))
def LF(): return list(map(float, stdin.readline().split()))
def LI_(): return list(map(lambda x: int(x)-1, stdin.readline().split()))
def II(): return int(stdin.readline())
def IF(): return float(stdin.readline())
def LS(): return list(map(list, stdin.readline().split()))
def S(): return list(stdin.readline().rstrip())
def IR(n): return [II() for _ in range(n)]
def LIR(n): return [LI() for _ in range(n)]
def FR(n): return [IF() for _ in range(n)]
def LFR(n): return [LI() for _ in range(n)]
def LIR_(n): return [LI_() for _ in range(n)]
def SR(n): return [S() for _ in range(n)]
def LSR(n): return [LS() for _ in range(n)]
mod = 1000000007
inf = float('INF')


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


def B():
    return


def C():
    return


def D():
    return


def E():
    return


def F():
    return


def G():
    return


def H():
    return


if __name__ == '__main__':
    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())
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 = 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):
i = list(map(int, input().split()))
a=i[0]
b=i[1]
c=i[2]
j_1 = b-a
j_2=c-b
if j_1==j_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())

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())

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())


ans = 'YES' if b - a == c - b else 'NO'


print(ans)

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

ab = b - a
bc = c - b

if ab == bc:
    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 a == 2*b-c else 'NO')

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

Solution (Python):
li = list(map(int,input().split()))
if (li[1]-li[0] == li[2]-li[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 or 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
sys.setrecursionlimit(300000)

YES = "YES"  
NO = "NO"  

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

Solution (Python):
a = list(map(int,input().split()))
if a[0]-a[1]==a[1]-a[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):
a,b,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 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):
nl = lambda: list(map(int, input().split()))
sl = lambda: input().split()
n = lambda: int(input())
s = lambda: input()

a, b, c = nl()
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):
x,y,z = map(int,input().split())
if z-y==y-x:
	print("YES")
else:
	print("NO")

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

Solution (Python):
a,b,c = map(int,input().split())
print(["NO","YES"][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):
l=input().split()
a,b,c=int(l[0]),int(l[1]),int(l[2])
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= 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())





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 = tuple(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):
import sys
input = sys.stdin.readline

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

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


abc()

Solution (Python):
s = list(map(int, input().split()))
if s[1] - s[0] == s[2] -s[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 = 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 = [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())
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 (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
def input(): return sys.stdin.readline().rstrip()
def mi(): return map(int, input().split())


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 =  [ int(v) for v in 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(' '))
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('%s' % 'YES' if b-a == c-b 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())
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())
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())
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 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 = input().split()
a, b, c = int(a), int(b), int(c)
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):
a,b,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 2*b==c+a else 'NO')

Solution (Python):
a,b,c=map(int,input().split());print('NYOE S'[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 copy
import random
import bisect 
import fractions 
import math

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=input().split()
a1=int(a)
b1=int(b)
c1=int(c)
d=b1-a1
e=c1-b1
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=input().split()
a1=int(a)
b1=int(b)
c1=int(c)
d=b1-a1
e=c1-b1
if d==e:
	print('YES')
else :
	print('NO')

Solution (Python):
x = list(map(int, input().split()))
X = sorted(x,reverse=True)
if X[0]-X[1] ==X[1]-X[2]:
    print("YES")
else:
    print('NO')

Solution (Python):
x = list(map(int, input().split()))
X = sorted(x,reverse=True)
if X[0]-X[1] ==X[1]-X[2]:
    print("YES")
else:
    print('NO')

Solution (Python):
x = list(map(int, input().split()))
X = sorted(x,reverse=True)
if X[0]-X[1] ==X[1]-X[2]:
    print("YES")
else:
    print('NO')

Solution (Python):
x = list(map(int, input().split()))
X = sorted(x,reverse=True)
if X[0]-X[1] ==X[1]-X[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):
x = list(map(int, input().split()))
X = sorted(x,reverse=True)
if X[0]-X[1] ==X[1]-X[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(lambda x: int(x), input().split(' '))
print('YES') if a - b == b - c  else print('NO')

Solution (Python):
x = list(map(int, input().split()))
X = sorted(x,reverse=True)
if X[0]-X[1] ==X[1]-X[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 = input().split()
a=int(a)
b=int(b)
c=int(c)
if b-a==c-b:
    print('YES')
else:
    print('NO')

Solution (Python):
i = input().split()
if int(i[1])-int(i[0]) == int(i[2])-int(i[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 (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 2*b == a+c:
    print("YES")
else:
    print("NO")

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

Solution (Python):
a=[int(i) for i in input().split()]
if (a[2]+a[0])/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):




import sys


class math:
    
    pi = 3.14159265358979323846264338

    
    def gcd(self, a, b):
        if b == 0:
            return a
        return self.gcd(b, a%b)

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

    
    def Pnum(self, a):
        if a == 1: return False
        for i in range(2,int(a**0.5)+1):
            if a % i == 0:
                return False
        return True

    
    def caria(self, r):
        return r*r*self.pi

math = math()


class output:
    
    def list(self, l):
        l = list(l)
        print(" ", end="")
        for i, num in enumerate(l):
            print(num, end="")
            if i != len(l)-1:
                print(" ", end="")
        print()

output = output()















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())

ans = "YES" if a-b == b-c 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 = 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 1 <= a and b and c <= 100:
    if b - a == c - b:
        print("YES")
    else:
        print("NO")

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

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

s = b - a
t = c - b

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

Solution (Python):
print((lambda a,b,c:"YNEOS"[a-2*b+c!=0::2])(*map(int,input().split())))

Solution (Python):
a, b, 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'][(a-b)==(b-c)])

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

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

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