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

 

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

  print('YES')

else:

  print('NO')
a,b,c = list(map(int,input().split()))

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

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

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

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