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

fn main() {
    let input = io::stdin()
        .lock()
        .lines()
        .map(|l| {
            l.unwrap()
                .split(' ')
                .map(|n| n.parse::<usize>().unwrap())
                .collect::<Vec<_>>()
        })
        .collect::<Vec<_>>();

    let sum = input[1].iter().sum::<usize>();
    if sum % 2 == 1 {
        println!("impossible");
    } else {
        let n = input[1].len();
        let goal = sum / 2;

        let mut possible = vec![vec![false; goal + 1]; n + 1];
        possible[0][0] = true;

        for i in 1..=n {
            for total in 0..=goal {
                possible[i][total] |= possible[i - 1][total];
                if input[1][i - 1] <= total {
                    possible[i][total] |= possible[i - 1][total - input[1][i - 1]];
                }
            }
        }

        println!("{}possible", if possible[n][goal] { "" } else { "im" });
    }
}