#include <bits/stdc++.h>

const long long MOD = 998244353;
int N;
long long A[300000];
long long sum = 0;

int main() {
    scanf("%d", &N);
    for (int i = 0; i < N; ++i) scanf("%lld", &A[i]);
    long long tmp = 1;
    for (int i = N - 1; i >= 0; --i) {
        sum = (sum + (MOD + tmp - 1) * A[i]) % MOD;
        tmp = tmp * 2 % MOD;
    }
    tmp = 1;
    for (int i = 0; i < N; ++i) {
        sum = (sum + MOD - (MOD + tmp - 1) * A[i] % MOD) % MOD;
        tmp = tmp * 2 % MOD;
    }
    printf("%lld\n", sum);
}