#![allow(unused_imports)]

use std::io::{self, BufRead};
use std::str::FromStr;
use std::collections::*;
use std::cmp::*;

struct Parser<'a> {
    tokens: &'a mut Iterator<Item = String>,
}

impl<'a> Parser<'a> {
    fn new(i: &'a mut Iterator<Item = String>) -> Self {
        Parser {tokens: i}
    }
    fn take<T: FromStr>(&mut self) -> T {
        match self.tokens.next().expect("empty iterator").parse() {
            Ok(x) => x,
            Err(_) => panic!()
        }
    }

    fn take_some<T: FromStr>(&mut self, n: usize) -> Vec<T> {
        self.tokens.take(n).map(|s| match s.parse() { Ok(x) => x, Err(_) => panic!() } ).collect()
    }
}

fn main() {
    let stdin = io::stdin();
    let mut tokens = stdin.lock().lines().filter_map(|x| x.ok()).flat_map(|x| x.split_whitespace().map(|s| s.to_owned()).collect::<Vec<String>>());
    let mut parser = Parser::new(&mut tokens);

    let n: i64 = parser.take();
    let w: Vec<i64> = parser.take_some(n as usize);

    let s: i64 = w.iter().sum();
    if s % 2 == 1 {
        println!("impossible");
        return;
    }
    let mut dp = Vec::new();
    dp.push(Vec::new());
    dp[0].resize(s as usize, false);
    dp[0][0] = true;
    for i in 0..n {
        let mut v = Vec::new();
        {
            let last = &dp[i as usize];
            for j in 0..s {
                v.push(last[j as usize] || (j - w[i as usize] >= 0 && last[(j-w[i as usize]) as usize]));
            }
        }
        dp.push(v);
    }
    println!("{}", if dp[n as usize][(s/2) as usize] {"possible"} else {"impossible"});
}