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):
ns=list(map(int, input().split()))
ns.sort()
if ns[0] + ns[2] == ns[1]*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 = map(int,raw_input().split())


if a[1] - a[0] == a[2] - a[1]:
        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 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):
b = input().split()
a = [int(b[i]) for i in range(len(b))]

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

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

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

if a-b == b - c:
    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 = [int(i) for i in input().split()]
print("YES" if a[1]*2==a[0]+a[2] 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 = 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):
import sys

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

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

Solution (Python):
a=input().split()
if int(a[1])*2==int(a[0])+int(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 = 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 = input().split()
a, b, c = int(a), int(b), int(c)

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

Solution (Python):
tmp = input().split()
a, b, c = int(tmp[0]), int(tmp[1]), int(tmp[2])

s1 = b - a
s2 = c - b

if s1 == s2:
    print('YES')
else:
    print('NO')

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

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

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

Solution (Python):
d=input().split()
a=int(d[0])
b=int(d[1])
c=int(d[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())
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
import numpy as np

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())
x1 = b-a
x2 = c-b
if(x1 == x2): 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):
numbers = list(map(int, input().split(' ')))
if numbers[2] - numbers[1] == numbers[1] - numbers[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())
d = b - a
e = c - b
if d == e:
  print("YES")
else:
  print("NO")

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

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

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

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

Solution (Python):
strs = input().split()
a = int(strs[0])
b = int(strs[1])
c = int(strs[2])

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

Solution (Python):
a, b, c = [int(i) for i in input().split(' ')]
if a+c==2*b:
    print('YES')
else:
    print('NO')

Solution (Python):
a,b,c=[int(i)for i 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):

length = list(map(int, input().split()))
if length[0] == 2*length[1] - length[2]:
    print('YES')

else:
    print('NO')

Solution (Python):
import sys

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

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

Solution (Python):
strs = input().split()
a = int(strs[0])
b = int(strs[1])
c = int(strs[2])

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

Solution (Python):
a,b,c = [int(i) for i in raw_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):
n = map(int, raw_input().split())

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

Solution (Python):
print 'YES' if (lambda l: l[2]-l[1] == l[1]-l[0] )([int(x) for x in raw_input().split()]) else 'NO'

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

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

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

Solution (Python):


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

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

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

Solution (Python):



raw = raw_input()
a = int(raw.split()[0])
b = int(raw.split()[1])
c = int(raw.split()[2])

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

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

l = min(a,b,c)
r = max(a,b,c)
m = a+b+c-l-r

print('YES' if m-l == r-m 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, raw_input().split())

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

Solution (Python):
from sys import stdin
a = map(int,stdin.readline().split())
a.sort()
ans = 'NO'
if a[0] + a[-1] == 2*a[1]:
 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 = [int(i) for i in 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:
    res = 'YES'
else:
    res = 'NO'
print(res)

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

mergin1=B-A
mergin2=C-B

if mergin1==mergin2:
 print 'YES'
else:
 print 'NO'

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

if (b-a) == (c-b):
    print("YES")

else:
    print("NO")

Solution (Python):


mozir=input()
hyo=mozir.split(' ')

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

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

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

Solution (Python):
n_vec = list(map(int, input().split()))
n1 = n_vec[0]
n2 = n_vec[1]
n3 = n_vec[2]
def abc_057_1(a,b,c):
    if b-a == c-b:
        return(print('YES'))
    else:
        return(print('NO'))
abc_057_1(n1,n2,n3)

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() ]
middle = (a + c)/2
 
if b == middle:
  print("YES")
else:
  print("NO")

Solution (Python):
import sys

x = sys.stdin.readline().strip().split(" ")

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

Solution (Python):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf = 10**20
mod = 10**9 + 7

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()


def main():
    a,b,c = LI()
    if c-b == b-a:
        return 'YES'
    return 'NO'



print(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, raw_input().split())

l = b - a
r = c - b

if l == r:
    print "YES"
else:
    print "NO"

Solution (Python):
a, b, 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, raw_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):
from __future__ import division
import io, sys, atexit, os, itertools
sys.stdout = io.BytesIO()
atexit.register(lambda: sys.__stdout__.write(sys.stdout.getvalue()))
sys.stdin = io.BytesIO(sys.stdin.read())
raw_input = lambda: sys.stdin.readline().rstrip()

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

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

Solution (Python):
strs = input().split()
a = int(strs[0])
b = int(strs[1])
c = int(strs[2])

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

Solution (Python):


if __name__ == '__main__':
    nums = input().split()
    if int(nums[1])-int(nums[0]) == int(nums[2])-int(nums[1]):
        print('YES')
    else:
        print('NO')

Solution (Python):
import sys

def main():
    line = sys.stdin.readline()
    a, b, c = [ int(i) for i in line.split() ]
    if b - a == c - b:
        print("YES")
    else:
        print("NO")

    return 0

if __name__ == '__main__':
    sys.exit(main())

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

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

Solution (Python):


import os
import sys
import math
import numpy as np

a, b, c = 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 c-b==b-a:
    print 'YES'
else:
    print 'NO'

Solution (Python):
l = input().split()

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

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

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

Solution (Python):
def main():
    a, b, c = map(int, input().split())
    x = abs(c + a) /2
    if b == x:
        print('YES')
    else:
        print('NO')

main()

Solution (Python):
abc = raw_input().split()
a = int(abc[0])
b = int(abc[1])
c = int(abc[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):


def list_n():
    return [int(e) for e in input().split()]



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

if __name__ == '__main__':
    a, b, c = list_n()
    print(main(a, b, c))

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

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

Solution (Python):

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

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

Solution (Python):
input_lines = str(input())
inputAry = input_lines.split(' ')

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

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

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

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

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

Solution (Python):
abc = input().split()
a = int(abc[0])
b = int(abc[1])
c = int(abc[2])
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 = list(map(int, input().split()))

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

Solution (Python):


if __name__ == "__main__":
    a, b, c = map(int, raw_input().split(" "))

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

Solution (Python):
def judge(a, b, c):
	if b - a == c - b:
		return 'YES'
	else:
		return 'NO'
		
inpt = map(int, raw_input().split())

print judge(inpt[0], inpt[1], inpt[2])

Solution (Python):


import sys
import os
import math


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

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

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

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

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

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

Solution (Python):
import sys
import math

INF = 10**9+7

stdin = sys.stdin
def na(): return map(int, stdin.readline().split())
def ns(): return stdin.readline().strip()
def nsl(): return list(stdin.readline().strip())
def ni(): return int(stdin.readline())
def nil(): return list(map(int, stdin.readline().split()))

a, b, c = nil()

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"