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

Solution (Python):

def read_input():
    a, b, c = map(int, input().split())
    return a, b, c


def submit():
    a, b, c = read_input()

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


if __name__ == '__main__':
    submit()

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 = [int(n) for n 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):
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(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):
import sys
a,b,c = list(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:
    print('YES')
elif a - b == b -c:
    peint('YES')
else:
    print('NO')

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

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

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

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

Solution (Python):


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

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

Solution (Python):
import functools

import os

INF = float('inf')


def inp():
    return int(input())


def inpf():
    return float(input())


def inps():
    return input()


def inl():
    return list(map(int, input().split()))


def inlf():
    return list(map(float, input().split()))


def inls():
    return input().split()


def inpm(line):
    return [inp() for _ in range(line)]


def inpfm(line):
    return [inpf() for _ in range(line)]


def inpsm(line):
    return [inps() for _ in range(line)]


def inlm(line):
    return [inl() for _ in range(line)]


def inlfm(line):
    return [inlf() for _ in range(line)]


def inlsm(line):
    return [inls() for _ in range(line)]


def debug(fn):
    if not os.getenv('LOCAL'):
        return fn

    @functools.wraps(fn)
    def wrapper(*args, **kwargs):
        print('DEBUG: {}({}) -> '.format(
            fn.__name__,
            ', '.join(
                list(map(str, args)) +
                ['{}={}'.format(k, str(v)) for k, v in kwargs.items()]
            )
        ), end='')
        ret = fn(*args, **kwargs)
        print(ret)
        return ret

    return wrapper

a, b, c = inl()
print('YES' if b-a == c-b else '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())
n = b - a
m = c - b
if n == m:
    print('YES')
else:
    print('NO')

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

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

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

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

Solution (Python):
import sys, os

f = lambda:list(map(int,input().split()))
if 'local' in os.environ :
    sys.stdin = open('./input.txt', 'r')

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

solve()

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

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

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

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

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

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

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

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

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

Solution (Python):
from functools import reduce
import math

def main():
    
    
    
    
    
    
    
    
    
    

    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    

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

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

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

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

Solution (Python):
import sys

def main():
    input = sys.stdin.readline
    A = list(map(int, input().split()))

    if A[1] - A[0] == A[2] - A[1]:
        return 'YES'
    else:
        return 'NO'


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


lis=list(map(int,input().split()))
lis_1=sorted(lis)

if lis_1[2] - lis_1[1] == lis_1[1] - lis_1[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())

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 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 print('NO')

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

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

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

Solution (Python):
a, b, 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):
def INSTR():
	return input()

def INNUM():
	return int(INSTR())

def INSTR_S():
	return INSTR().split()

def INNUM_S():
	return map(int, INSTR_S())

def INSTR_SM(n):
	return [tuple(INSTR_S()) for _ in range(n)]

def INNUM_SM(n):
	return [tuple(INNUM_S()) for _ in range(n)]

A, B, C = INNUM_S()
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())
print("YNEOS"[a-b!=b-c::2])

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

Solution (Python):
def lll(a: int, b: int, c: int)->bool:
    return c-b == b-a


if __name__ == "__main__":
    a, b, c = map(int, input().split())
    yes = lll(a, b, c)
    print('YES' if yes else 'NO')

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

Solution (Python):

from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS():return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = I()
    return l
def LIR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = LI()
    return l
def SR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = S()
    return l
def LSR(n):
    l = [None for i in range(n)]
    for i in range(n):l[i] = SR()
    return l
mod = 1000000007


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



"""
n = I()
s = SR(n)
for i in range(n):
    for j in range(len(s[i])):
        while s[i][j] in s[i][:j]:
            s[i][j] = "0"+s[i][j]
ans = set(s[0])
for i in range(1,n):
    ans &= set(s[i])
ans = sorted(list(ans))
if len(ans) == 0:print()
else:
    for i in range(len(ans)):
        ans[i] = ans[i][-1]
    ans.sort()
    for i in range(len(ans)-1):
        print(ans[i],end = "")
    print(ans[-1])
"""


"""
n,m = LI()
ln = [n-1]
lm = [m-1]
a = n-1
b = m-1
while a > 2:
    a -= 2
    ln.append(ln[-1]+a)
while b > 2:
    b -= 2
    lm.append(lm[-1]+b)
la = len(ln)
lb = len(lm)
for i in range(la):
    if i or a == 2:
        ln.append(ln[la-i-1])
for i in range(lb):
    if i or b == 2:
        lm.append(lm[lb-i-1])
x,y = LIR(2)
lx = 0
ly = 0
for i in range(n-1):
    lx += ln[i]*(x[i+1]-x[i])%mod
    lx %= mod
for i in range(m-1):
    ly += lm[i]*(y[i+1]-y[i])%mod
    ly %= mod
ans = lx*ly%mod
print(ans)
"""

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

Solution (Python):


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

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

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

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

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

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

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

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 = [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 = list(map(int, input().split()))

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

Solution (Python):

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

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

Solution (Python):
a, b, c = map(int, input().split())
print('YES' if b - a == c - b else '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())

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):

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 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 a+c==b*2: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 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(2*b == a+c):
    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=(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())

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

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

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

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

Solution (Python):
a=[int(i) for i in input().split()]
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())

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):
from sys import stdin
a, b, c = [int(x) for x in stdin.readline().rstrip().split()]
if (b-a) == (c-b):
  print('YES')
else:
  print('NO')

Solution (Python):
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 print("NO")

Solution (Python):


"""
ι⊥l（柱）
"""

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


def main():
    beautiful()


if __name__ == '__main__':
    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())
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('YNEOS'[b-a!=c-b::2])

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

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

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

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

ans =  (b - a) == (c - b)

print("YES" if ans else "NO")
print()

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

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

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

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

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

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

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

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

if abc[1]-abc[0]==abc[2]-abc[1]:
    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 a+c==b*2:
  print("YES")
else:
  print("NO")

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Solution (Python):
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):
""" AtCoder """

a, b, 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())
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 = [int(_) for _ 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 = [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 = (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 = [int(x) for x in input().split()]

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

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

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

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

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

Solution (Python):
x=input().split()
if int(x[0]) + int(x[2]) == int(x[1]) * 2:
    print("YES")
else:
    print("NO")

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

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

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

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

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

Solution (Python):
int_a, int_b, int_c = map(int, 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 a+c==2*b else 'NO')

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

Solution (Python):
a, b, c = 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 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):
def abc058_a():
    a, b, c = map(int, input().split())
    if (b - a) == (c - b):
        print("YES")
    else:
        print("NO")


abc058_a()

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

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


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

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

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

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):
s=input().split()
if(int(s[0])-int(s[1])==int(s[1])-int(s[2])):
    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())
l = b - a
r = c - b
if(l == r):
  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 = [int(i) for i in input().split() ]
print("YES" if 2*b == a+c 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 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):
abc=list(map(int,input().split()))
abc.sort(reverse=True)
if abc[0]-abc[1]==abc[1]-abc[2]:
    print("YES")
else:
    print("NO")

Solution (Python):
from statistics import mean, median,variance,stdev
import sys
import math

x = input().split()

a = []
for i in range(len(x)):
   a.append(int(x[i]))
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):



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

Solution (Python):

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

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

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

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

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

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

print('YES' if (t[1] - t[0] == t[2] - t[1]) else 'NO')

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

Solution (Python):
a=input().strip().split(" ")

b=[int(i) for i in a]

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

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

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

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

Solution (Python):
a = 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());print('YNEOS'[b-a!=c-b::2])

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

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

Solution (Python):
a,b,c = 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')