import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        long[] a = new long[n];
        long mod = 998244353;
        for(int i = 0; i < n; i++){
            a[i] = sc.nextLong();
        }
        long ans = 0;
        for(int i = 0; i < n; i++){
            long cntL = rep2(2,i,mod);
            long cntR = rep2(2,n-1-i,mod);
            cntL = (cntL+mod-1) % mod;
            cntR = (cntR+mod-1) % mod;
            ans += (a[i]*cntR) % mod;
            ans %= mod;
            ans -= (a[i]*cntL) % mod;
            if(ans < 0) ans += mod;
        }
        System.out.println(ans);
    }
    
    private static long rep2(long b, long n, long mod){
        if(n == 0) return 1;
        long bn = rep2(b,n/2,mod);
        if(n % 2 == 0){
            return (bn*bn)%mod;
        }else{
            return (bn*bn)%mod*b%mod;
        }
    }
}