mod = 998244353
eps = 10**-9


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

    N, M = map(int, input().split())

    ans = 0
    K = [0] * (M+1)
    L = [(M * (M+1) // 2)%mod] * (M+1)
    for i in range(1, M+1):
        K[i] = (K[i-1] + i)%mod
        L[i] = (L[i-1] - (i - 1))%mod
    L.append(0)
    for i in range(1, M+1):
        ans = (ans + (i * ((K[i] * pow(i, N-1, mod) * N)%mod - (K[i-1] * pow(i-1, N-1, mod) * N)%mod)%mod)%mod)%mod
        ans = (ans - (i * ((L[i] * pow(M - i + 1, N - 1, mod) * N)%mod - (L[i + 1] * pow(M - i, N - 1, mod) * N)%mod) % mod)%mod)% mod
    print(ans)


if __name__ == '__main__':
    main()