use std::io::{stdin, BufRead};

fn main() {
    let stdin = stdin();
    let mut stdin = stdin.lock().lines().map(Result::unwrap);
    let _n = stdin.next().unwrap().parse::<usize>().unwrap();
    let w = stdin
        .next()
        .unwrap()
        .split_whitespace()
        .map(|x| x.parse::<usize>().unwrap())
        .collect::<Vec<_>>();
    let lim = w.iter().sum::<usize>() + 1;
    let mut dp = vec![false; lim];
    dp[0] = true;
    for &w in &w {
        for i in (0..lim - w).rev() {
            dp[i + w] |= dp[i];
        }
    }
    let ans = lim % 2 == 1 && dp[lim / 2];
    println!("{}", ["impossible", "possible"][ans as usize]);
}