x1, v1, x2, v2 = map(int, input().strip().split()) count = 0 for i in range(10000): if v2> v1: break

x1 += v1
x2 += v2
if x1 == x2:
    print('YES')
    count += 1
    break
if x1 > x2 :
    break

if count == 0: print('NO')