#include<bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353; //1000000007;
using ll=long long;
using pp=pair<int,int>;
#define sr string 
#define vc vector
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define pque priority_queue
#define bpc(a) __builtin_popcount(a)
int main(){
  ll n,m;cin>>n>>m;
  mint ans=0;
  for(ll d=1;d<m;d++){
    mint res=mint(d+1).pow(n)-mint(d).pow(n)*2+mint(d-1).pow(n);
    res*=(mint)n*(1+m)/2*(m-d);
    ans+=res*d;
  }
  cout<<ans.val();
}