Problem:
 Score : 100 points    Problem Statement Three poles stand evenly spaced along a line. Their heights are a , b and c meters, from left to right.
We will call the arrangement of the poles beautiful if the tops of the poles lie on the same line, that is, b-a = c-b .  Determine whether the arrangement of the poles is beautiful.      Constraints  1 \leq a,b,c \leq 100  a , b and c are integers.         Input Input is given from Standard Input in the following format:  a  b  c       Output Print YES if the arrangement of the poles is beautiful; print NO otherwise.        Sample Input 1 2 4 6      Sample Output 1 YES  Since 4-2 = 6-4 , this arrangement of poles is beautiful.       Sample Input 2 2 5 6      Sample Output 2 NO  Since 5-2 \neq 6-5 , this arrangement of poles is not beautiful.       Sample Input 3 3 2 1      Sample Output 3 YES  Since 1-2 = 2-3 , this arrangement of poles is beautiful.

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

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

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

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

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

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

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

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

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

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

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

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

Solution (Python):

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

Solution (Python):
a, b, c = map(int, input().split())
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):
n = input().split()
a, b, c = int(n[0]), int(n[1]), int(n[2])
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,input().split());print('YNEOS'[b-a!=c-b::2])

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):
from collections import defaultdict, Counter
from itertools import product, groupby, count, permutations, combinations
from math import pi, sqrt
from collections import deque
from bisect import bisect, bisect_left, bisect_right
from string import ascii_lowercase
from functools import lru_cache
import sys
sys.setrecursionlimit(10000)
INF = float("inf")
YES, Yes, yes, NO, No, no = "YES", "Yes", "yes", "NO", "No", "no"
dy4, dx4 = [0, 1, 0, -1], [1, 0, -1, 0]
dy8, dx8 = [0, -1, 0, 1, 1, -1, -1, 1], [1, 0, -1, 0, 1, 1, -1, -1]


def inside(y, x, H, W):
    return 0 <= y < H and 0 <= x < W


def ceil(a, b):
    return (a + b - 1) // b


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

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

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

Solution (Python):
a, b, c = list(map(int, input().split()))
if a-b == b-c:
  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):
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())
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*2-a-c!=0::2])

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(' YNEOS'[b-a==c-b::2])

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

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

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

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

Solution (Python):
a,b,c = 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 b-a==c-b:
    print('YES')
else:
    print('NO')

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

if __name__ == '__main__':
    main()

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

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

Solution (Python):
def main14():
    buf = input("");
    bufs = buf.split();
    hai = [];
    for i in range(len(bufs)):
        hai.append(int(bufs[i]));
    if hai[1] - hai[0] == hai[2] - hai[1]:
        print("YES");
    else:
        print("NO");

if __name__ == '__main__':
    main14()

Solution (Python):
a, b, 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 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())
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):


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())
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):
a, b, 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 (b - a) == (c - b) else "NO")

Solution (Python):
a,b,c=map(int,input().split())
print('YES' if a+c==b*2 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())
d1 = a-b
d2= b-c
if d1 == d2:
 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):

n=[int(i) for i in input().split()]
if(n[1]-n[0]==n[2]-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):
l = [int(x) for x in raw_input().split()]
print "YES" if 2*l[1] == l[0] + l[2] else "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=map(int,input().split())
if 2*b==c+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())
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=map(int,input().split())
print("YES" if b-a==c-b else "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())
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())
print("YES" if b-a==c-b else "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 = (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(["NO","YES"][b-a == c-b])

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

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

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

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

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

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

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

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

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

if 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())
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):
ina,inb,inc = map(int,input().split())
if inb - ina == inc - inb:
  print("YES")
else:
  print("NO")

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 == b*2:
    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 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())
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):





if __name__ == '__main__':
    a, b, c = list(map(int, input().split()))

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

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

Solution (Python):
import math
import sys

def getinputdata():

    
    array_result = []
    
    data = input()

    
    array_result.append(data.split(" "))

    flg = 1

    try:


        while flg:

            data = input()

            array_temp = []

            if(data != ""):
                
                array_result.append(data.split(" "))

                flg = 1

            else:

                flg = 0
    finally:


        return array_result





arr_data = getinputdata()

a = int(arr_data[0][0])
b = int(arr_data[0][1])
c = int(arr_data[0][2])


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(s) for s in 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):
import sys

stdin = sys.stdin

ni = lambda: int(ns())
na = lambda: list(map(int, stdin.readline().split()))
ns = lambda: stdin.readline()

a,b,c = na()
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 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 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=[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 = map(int, raw_input().split())

if sum(a)==a[1]*3:
    print "YES"
else:
    print "NO"

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):

"""
https://abc058.contest.atcoder.jp/tasks/abc058_a

"""
import sys
from sys import stdin
input = stdin.readline


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


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


if __name__ == '__main__':
    main(sys.argv[1:])

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

if (b - a) + 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):





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

if __name__ == "__main__": main()

Solution (Python):
a, b, c = [int(x) for x in 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):
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(['NO','YES'][b-a==c-b])

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

Solution (Python):
print(("NO","YES")[sum(int(x)*y for x,y in zip(input().split(),[1,-2,1])) == 0])

Solution (Python):
n = input().split()
m = list(map(int, n))
if m[1] - m[0] == m[2] - m[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):
def solve():
    a, b, c = list(map(int, input().split(" ")))

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


solve()

Solution (Python):
a,b,c=map(int,raw_input().split())
print "YES" if b-a==c-b else "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())
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):
num = [int(x) for x in input().split()]

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

Solution (Python):


a,b,c=list( int(i) for i in input().split() )

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

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

A = ls[0] - ls[1]
B = ls[1] - ls[2]

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

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

Solution (Python):
a,b,c = map(int,raw_input().split())
if b+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, raw_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 = [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):
xs = list(map(int, input().split()))

if xs[1] - xs[0] == xs[2] - xs[1]:
    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):
def read_int_list():
    return list(int(i) for i in input().split())
    
a,b,c = read_int_list()
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, raw_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):
def main():
    a, b, c = map(int, input().split())
    if a-b == b-c: 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):
def inint(): return int(input())
def inlint(): return list(map(int, input().split()))
def infloat(): return float(input())
def inlffloat(): return list(map(float, input().split()))
def inl(): return list(input())
def putlint(): return "".join(list(map(str, ans)))

a,b,c = inlint()

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

Solution (Python):
input_line1 = map(int,raw_input().split(" "))


a = input_line1[0]
b = input_line1[1]
c = input_line1[2]

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

Solution (Python):

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

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

Solution (Python):
hstr = input().split()
h = []
for i in hstr:
    h.append(int(i))
if h[1]-h[0] == h[2]-h[1]:
    print('YES')
else:
    print('NO')

Solution (Python):
from collections import defaultdict


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):
l = list(map(int, input().split()))
if 2 * l[1] - l[0] == l[2]:
    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 2 * b == a + c:
    print("YES")
else:
    print("NO")

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

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

if __name__ == "__main__":
    solve()

Solution (Python):


if __name__ == '__main__':
    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):
def solve():
    a, b, c = map(int, input().split())
    if b - a == c - b:
        ans = "YES"
    else:
        ans = "NO"
    print(ans)

if __name__ == "__main__":
    solve()

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

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

c1 = int(tmp_n[1]) - int(tmp_n[0])
c2 = int(tmp_n[2]) - int(tmp_n[1])

if c1 == c2:
    print("YES")
else:
    print("NO")

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

Solution (Python):
(lambda x: print('YES') if x[1] - x[0] == x[2] - x[1]  else print('NO'))(list(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())

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

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

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

Solution (Python):
a, b, c = [int(t) for t 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, raw_input().split())
print "YES" if ((b - a) == (c - b)) else "NO"

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

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

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