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

const MAX: usize = 100*100;

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

    let lines: Vec<_> = stdin.lock().lines().map(|r| r.unwrap()).collect();
    let mut reachable: Vec<bool> = std::iter::repeat(false).take(MAX).collect();
    reachable[0] = true;
    let sum = lines[1].split_whitespace().map(|s| s.parse::<usize>().unwrap()).map(|v| {
        for i in (0..reachable.len()).rev() {
            if reachable[i] && i + v < reachable.len() {
                reachable[i + v] = true;
            }
        }; v}).fold(0, |acc, item| acc + item);
    println!("{}", if sum % 2 == 0 && reachable[sum / 2] {"possible"} else {"impossible"});

}