#include <bits/stdc++.h>

#include <atcoder/modint>
using namespace std;
using mint = atcoder::modint998244353;

mint res;
int main() {
	long long n;
	int m;
	cin >> n >> m;
	for(int diff = 1; diff < m; diff++) {
		mint tmp = mint(diff + 1).pow(n) - mint(diff).pow(n) * 2 + mint(diff - 1).pow(n);
		res += tmp * diff * (m - diff);
	}
	res *= n;
	res *= m + 1;
	res /= 2;
	cout << res.val() << '\n';
}