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