try:
    a, b, m, n = map(float, input().split())
except Exception:
    print("Ошибка: введите 4 числа через пробел")
    raise SystemExit(1)

if m > n:
    m, n = n, m

if a == 0:
    print("YES" if b == 0 else "NO")
else:
    x = -b / a
    print("YES" if m <= x <= n else "NO")