def main():
    L, R, M, K = map(int, input().split())
    if L == 0 or K == 0:
        return True

    L = L * K
    R = R * K
    dl, ml = divmod(L, M)
    dr, mr = divmod(R, M)
    if dl != dr:
        return True
    return ml == 0


if main():
    print("Yes")
else:
    print("No")