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-a:
    print("YES")
else:
    print("NO")

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