use std::io;
use std::io::BufRead;

fn main() {
    let stdin = io::stdin();

    let input: Vec<_> = stdin.lock().lines().map(|r| r.unwrap()).collect();

    let w: Vec<u32> = input[1].split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = w.len() as u32;


    println!("{}", if is_possible(0, 0, 0, n, &w) {"possible"} else {"impossible"});
}

fn is_possible(num_used: u32, wl: u32, wr: u32, n: u32, ws: &[u32]) -> bool {
    if num_used == n {
        return wr == wl;
    }
    let num_used_next = num_used + 1;
    let w = ws[num_used as usize];
    return is_possible(num_used_next, wl + w, wr, n, ws) ||
        is_possible(num_used_next, wl, wr + w, n, ws);
}