#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000001

int main(){
	
	ios::sync_with_stdio(false);
	std::cin.tie(nullptr);
	
	int n;
	cin>>n;
	vector<long long> a(n);
	rep(i,n)cin>>a[i];
	
	vector<mint> dp(6,0);
	dp[0] = 1;
	rep(i,n){
		vector<mint> ndp(6,0);
		ndp[0] += dp[0];
		ndp[1] += dp[0] + dp[1];
		ndp[3] += dp[3] + (dp[0] + dp[1] + dp[2]) * a[i];
		ndp[4] += dp[3] + dp[4];
		rep(j,6)ndp[j] += dp[j];
		ndp[2] = 0;
		swap(dp,ndp);
	}
	
	mint ans = dp[3] + dp[4] + dp[5];
	cout<<ans.val()<<endl;
	
	
	return 0;
}