#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for(int i=0;i<(n);i++)
#define Inf 1000000001


int main(){
	
	int N,M;
	cin>>N>>M;
	
	vector dp(N+1,vector<mint>(M+1,0));
	dp[0][0] = 1;
	vector<mint> sum(N+1,0);
	sum[0] = 1;
	for(int i=1;i<=N;i++){
		for(int j=1;j<=M;j++){
			mint v = sum[i-1];
			if(i-j>=0)v -= sum[i-j];
			v -= dp[i-1][j];
			if(i-j>=0)v += dp[i-j][j];
			dp[i][j] = v;
			dp[i][j] += dp[i-1][j];
			sum[i] += v;
		}
		sum[i] += sum[i-1];
	}
	mint ans = sum.back();
	ans -= sum[N-1];
	ans = mint(M).pow(N) - ans;
	cout<<ans.val()<<endl;
	
	return 0;
}