use std::io::*;
const MOD: u64 = 1000000007;
fn mod_pow(mut x: u64, mut e: u64, m: u64) -> u64 {
    let mut res = 1;
    while e > 0 {
        if e & 1 == 1 {
            res = res * x % m;
        }
        x = x * x % m;
        e >>= 1;
    }
    res
}
fn main() {
    let mut s: String = String::new();
    std::io::stdin().read_to_string(&mut s).ok();
    let mut itr = s.trim().split_whitespace();
    let n: usize = itr.next().unwrap().parse().unwrap();
    let a: Vec<u64> = (0..n)
        .map(|_| itr.next().unwrap().parse().unwrap())
        .collect();

    let mut ans = 0u64;
    let mut mul = 1u64;
    for i in 0..n {
        mul *= a[i];
        mul %= MOD;
        if i == n - 1 {
            ans += mul;
        } else {
            ans += mul * 2 % MOD * mod_pow(3, n as u64 - 2 - i as u64, MOD) % MOD;
        }
        ans %= MOD;
    }

    println!("{}", ans);
}