#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;

long long md = 998244353, r2;

long long fp(long long n, long long k)
{
	long long s = 1;
	while (k) {
		if (k & 1) s = (s * n) % md;
		n = (n * n) % md; k /= 2;
	}
	return s;
}

long long sp(long long a, long long d, long long n)
{
	long long t = (a * 2 + d * (n - 1)) % md;
	return (((t * r2) % md) * n) % md;
}

int main()
{ 
	ios::sync_with_stdio(false);
	cin.tie(0);
	long long n, m; cin >> n >> m;
	long long ans = 0;
	r2 = fp(2, md - 2);
	if (m == 1 || n == 1) {
		cout << 0 << '\n';
		return 0;
	}
	for (long long i = 1; i < m; i++) {
		long long s = 0;
		long long p0 = (fp(i + 1LL, n - 1LL) - fp(i, n - 1LL) * 2 + fp(i - 1LL, n - 1LL) + md * 2) % md;
		long long p1 = (fp(i + 1LL, n - 1LL) - fp(i, n - 1LL) + md) % md;
		s = (p0 * sp((i * (i + 1LL) / 2 - 1LL) % md, i - 1LL, m - i)) % md;
		s = (s + p1 * sp(i + 2LL, 2LL, m - i)) % md;
		s = (s * i) % md;
		ans = (ans + s) % md;
	}
	ans = (ans * (n % md)) % md;
	cout << ans << '\n';
	return 0;
}