N, M = map(int, input().split())
MOD = 998244353


def tri(x):
    return x * (x + 1) // 2


def fix_max(k):
    return k * N * (tri(k) * pow(k, N - 1, MOD) - tri(k - 1) * pow(k - 1, N - 1, MOD)) % MOD


def fix_min(k):
    return k * N * ((tri(M) - tri(k - 1)) * pow(M - k + 1, N - 1, MOD) - (tri(M) - tri(k)) * pow(M - k, N - 1, MOD)) % MOD


ans = 0
for k in range(1, M + 1):
    # print(k, fix_max(k), fix_min(k))
    ans += fix_max(k)
    ans -= fix_min(k)
    ans %= MOD
print(ans)