## https://yukicoder.me/problems/no/3095

MOD = 998244353

def main():
    N, M = map(int, input().split())

    m_n = pow(M, N, MOD)

    answer = N
    for m in range(2, M + 1):
        p = ((M + 1 - m) * pow(M, MOD -2, MOD)) % MOD

        x1 = pow(p, N, MOD)
        x1 = (1 - x1) % MOD
        x2 = (1 - p) % MOD

        ans = (x1 * p) % MOD
        ans *= pow(x2, MOD - 2, MOD)
        ans %= MOD

        answer += ans
    
    answer *= m_n
    answer %= MOD
    print(answer)









if __name__ == '__main__':
    main()