#include <bits/stdc++.h>
using namespace std;
const int mod = 998244353;
int n, m;
int Power(int x, int y) {
	int r = 1;
	while (y) {
		if (y & 1) r = 1ll * r * x % mod;
		x = 1ll * x * x % mod, y >>= 1;
	}
	return r;
}
int f[500005][5][5];
void upd(int &x, int y) { x = (x + y) % mod; }
int Get(int n, int m) {
	memset(f, 0, sizeof(f));
	for (int i = 0; i <= m; i++) {
		f[1][i][i] = 1;
	}
	for (int i = 1; i < n; i++) {
		for (int j = 0; j <= m; j++) {
			for (int k = 0; k <= m; k++) {
				for (int l = max(j - k, 0); l <= m; l++) {
					upd(f[i + 1][l][k - max(j - l, 0)], f[i][j][k]);
				}
			}
		}
	}
	int ans = 0;
	for (int j = 0; j <= m; j++)
		for (int k = 0; k <= m; k++) upd(ans, f[n][j][k]);
	return ans;
}
int h[500005];
int main() {
	cin >> n >> m;
	if (m <= 2) return cout << Get(n, m) << endl, 0;
	h[1] = Get(n, 1);
	h[2] = Get(n, 2);
	for (int i = 3; i <= m; i++) {
		int v1 = (mod - 1ll * n * (n + 1) % mod + mod - 2ll * i * i % mod) % mod;
		int v2 = (1ll * i * i - i + mod) % mod;
		h[i] = (mod - (1ll * v1 * h[i - 1] + 1ll * v2 * h[i - 2]) % mod * Power(i, mod - 2) % mod *
		                  Power(i + 1, mod - 2) % mod) %
		       mod;
	}
	cout << h[m];
}