use std::io::*;

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 mut a: Vec<i64> = (0..n + 1)
        .map(|_| itr.next().unwrap().parse().unwrap())
        .collect();

    for i in (3..n + 1).rev() {
        a[i - 2] += a[i];
        a[i] = 0;
    }
    while a.last().unwrap() == &0 {
        a.pop();
    }

    if a.len() == 0 {
        println!("0");
        println!("0");
        return;
    }
    let mut out = Vec::new();
    writeln!(out, "{}", a.len() - 1).ok();
    for i in 0..a.len() {
        if i == a.len() - 1 {
            writeln!(out, "{}", a[i]).ok();
        } else {
            write!(out, "{} ", a[i]).ok();
        }
    }
    stdout().write_all(&out).unwrap();
}