MOD = 998244353
N, M = map(int, input().split())
ans = 0
def s(x):
    return (x * (x + 1) // 2) % MOD
for m in range(1, M + 1):
    tmp = s(m) * pow(m, N - 1, MOD) - s(m - 1) * pow(m - 1, N - 1, MOD)
    tmp %= MOD
    ans = (ans + m * tmp % MOD * N) % MOD
    tmp = (s(M) - s(m - 1)) * pow(M - m + 1, N - 1, MOD) - (s(M) - s(m)) * pow(M - m, N - 1, MOD)
    tmp %= MOD
    ans = (ans - m * tmp % MOD * N) % MOD
print(ans)