#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<long long> VL;
typedef vector<VL> VVL;
typedef long long LL;
#define all(a) (a).begin(), (a).end()
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define ALL(a)  (a).begin(),(a).end()

#include <atcoder/modint>
using mint = atcoder::modint998244353;


int main() {
  int n; cin>>n;
  int A[n];
  rep(i,n){cin>>A[i];}
  mint ans=A[0]+1;
  mint fac[200001];
  fac[0]=1;
  for(int i=1;i<=200000;i++){
    fac[i]=fac[i-1]*i;
  }
  for(int i=1;i<n;i++){
    rep(j,A[i]){
      ans+=fac[i+j]/(fac[i]*fac[j]);
    }
  }
  cout<<ans.val()<<endl;
}