#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

struct combi{
	deque<mint> kaijou;
	deque<mint> kaijou_;
	
	combi(int n){
		kaijou.push_back(1);
		for(int i=1;i<=n;i++){
			kaijou.push_back(kaijou[i-1]*i);
		}
		
		mint b=kaijou[n].inv();
		
		kaijou_.push_front(b);
		for(int i=1;i<=n;i++){
			int k=n+1-i;
			kaijou_.push_front(kaijou_[0]*k);
		}
	}
	
	mint combination(int n,int r){
		if(r>n)return 0;
		mint a = kaijou[n]*kaijou_[r];
		a *= kaijou_[n-r];
		return a;
	}
	
	mint junretsu(int a,int b){
		mint x = kaijou_[a]*kaijou_[b];
		x *= kaijou[a+b];
		return x;
	}
	
	mint catalan(int n){
		return combination(2*n,n)/(n+1);
	}
	
};

int main(){
	
	combi C(1000000);
	mint ans = 0;
	
	int N,M;
	cin>>N>>M;
	
	ans = mint(M).pow(N*2);
	ans *= M;
	
	for(int t=1;t<=200005;t++){
		if(t-1>N)break;
		mint temp = C.combination(N,t-1);		
		temp *= mint(2).pow(t-1);
		if(t>M)break;
		temp *= C.combination(M,t);
		temp *= C.kaijou[t-1];
		temp *= mint(M-t).pow((N-(t-1))*2);
		if(t>=3){
			temp *= mint(t).pow(t-2);
		}
		ans -= temp;		
	}
	
	cout<<ans.val()<<endl;
	
	return 0;
}