#include<bits/stdc++.h>
#include<atcoder/modint>
using namespace std;

int main(){
  using mint=atcoder::modint998244353;
  int x;
  cin>>x;
  vector<mint> y(x);
  vector<mint> s(x);
  mint sum=0;
  mint n=1;
  for (int i=0;i<x;i++){
    int y2;
    cin>>y2;
    y[i]=y2;
    s[i]=y[i]*(y[i]+1)/2;
    sum+=s[i];
    n+=y[i];
  }
  mint ans=0;
  for (int i=0;i<x;i++){
    ans+=n*s[i];
    ans-=(2*y[i]+1)*(y[i]+1)*y[i]/6;
  }
  cout<<ans.val()<<endl;
}