use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();
    
    let mut iter = buf.split_whitespace().map(|w| w.parse::<usize>().unwrap());
    
    iter.next().unwrap();
    let weights = iter;
    
    let mut remaining: usize = weights.clone().sum();
    if remaining % 2 == 1 {
        println!("impossible");
        return
    }
    
    let half: usize = remaining / 2;
    let mut sums: Vec<usize> = vec![0];
    
    for weight in weights {
        let mut new_sums: Vec<usize> = Vec::new();
        remaining -= weight;
        
        for sum in sums.into_iter() {
            let new_sum: usize = sum + weight;
            if new_sum <= half {
                new_sums.push(new_sum);
            }
            if remaining + sum >= half {
                new_sums.push(sum);
            }
        }
        new_sums.sort();
        new_sums.dedup();
        sums = new_sums;
    }
    
    println!("{}", if sums.contains(&half) {"possible"} else {"impossible"});
}