#include <iostream>
using namespace std;
typedef long long ll;

const ll MOD = 998244353;

ll modpow(ll x, ll n){
    ll res = 1, r = x;
    while(n){
        if(n & 1) res = res * r % MOD;
        r = r * r % MOD;
        n >>= 1;
    }
    return res;
}

ll foo(ll m, ll n){
    ll s = m * (m + 1) / 2 % MOD;
    return s * modpow(m, n - 1) % MOD * (n % MOD) % MOD;
}

ll foo2(ll m, ll i, ll n){
    ll s = (m * (m + 1) / 2 - i * (i - 1) / 2) % MOD;
    return s * modpow(m - i + 1, n - 1) % MOD * (n % MOD) % MOD;
}

int main()
{
    ll n, m;
    cin >> n >> m;
    ll ans = 0;
    for(ll i = m; i > 0; i--){
        ans = (ans + (foo(i, n) - foo(i - 1, n) + MOD) * i) % MOD;
    }
    for(ll i = 1; i <= m; i++){
        ans = (ans - foo2(m, i, n) + MOD) % MOD;
    }
    cout << ans << endl;
}