use std::collections::VecDeque;

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

    while a.len() > 1 {
        let lim = a.len() - 1;
        for _ in 0..lim {
            let mut temp = a.pop_front().unwrap();
            temp += a.front().unwrap();
            a.push_back(temp);
        }
        a.pop_front();
    }

    println!("{}", a[0] % 1_000_000_007);
}