mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    L, R, mod, K = map(int, input().split())

    if K == 0:
        print("Yes")
        exit()

    if R*K - L*K >= mod-1:
        print("Yes")
    else:
        if (L*K)%mod > (R*K)%mod or (L*K)%mod == 0:
            print("Yes")
        else:
            print("No")


if __name__ == '__main__':
    main()