const MOD: usize = 998244353;

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut p2s = vec![1usize; n+1];
    for i in 0..n { p2s[i+1] = p2s[i] * 2 % MOD; }
    let mut summary = vec![0usize; n+1];
    for i in 0..n {
        summary[i+1] = summary[i] + p2s[i];
        summary[i+1] %= MOD;
    }
    let mut result = 0usize;
    for i in 0..n {
        if i+1 < n {
            result += summary[n-1-i] * a[i] % MOD;
            result %= MOD;
        }
        if i > 0 {
            result += MOD - summary[i] * a[i] % MOD;
            result %= MOD;
        }
    }
    println!("{}", result);
}