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"))