def main():
    X, Y = map(int, input().split())
    N = int(input())
    A_list = list(map(int, input().split()))

    for i in range(N - 1):
        t1 = A_list[i] / X
        t2 = A_list[i + 1] / Y
        if t1 > t2:
            print("NO")
            break
    else:
        print("YES")


if __name__ == '__main__':
    main()