// No.2111 Sum of Diff
package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Buffer(make([]byte, 200_000*10+2), 200_000*10+2)
	sc.Scan()
	N, _ := strconv.Atoi(sc.Text())

	sc.Scan()
	ss := strings.Split(sc.Text(), " ")

	sum := 0
	for i, s := range ss {
		a, _ := strconv.Atoi(s)
		k := modpow(2, N-1-i, MOD) - modpow(2, i, MOD)
		v := (k * a % MOD)
		if v < 0 {
			v += MOD
		}
		sum = (sum + v) % MOD
	}

	fmt.Println(sum)
}

const MOD = 998244353

func modpow(a int, n int, mod int) int {
	m := 1
	for n > 0 {
		if n&1 == 1 {
			m = (m * a) % mod
		}
		a = (a * a) % mod
		n >>= 1
	}
	return m
}