#include<cstdio>
#include<atcoder/modint>
using namespace std;
using namespace atcoder;
using Mint = modint998244353;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)

int main(){
    int N;
    scanf("%d", &N);
    Mint two[N];
    two[0] = 1;
    rep(i, N-1) two[i+1] = two[i]*2;
    Mint answer{0};
    rep(i, N){
        int A;
        scanf("%d", &A);
        answer += Mint::raw(A)*(two[N-1-i] - two[i]);
    }
    printf("%u\n", answer.val());
    return 0;
}