import java.io.*;
import java.util.*;

public class Main {
    static int[] weight;
    static ArrayList<HashSet<Integer>> dp = new ArrayList<>();
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        weight = new int[n];
        for (int i = 0; i < n; i++) {
            weight[i] = sc.nextInt();
            dp.add(new HashSet<>());
        }
        if (dfw(n - 1, 0)) {
            System.out.println("impossible");
        } else {
            System.out.println("possible");
        }
    }
    
    static boolean dfw(int idx, int w) {
        if (idx < 0) {
            return w != 0;
        }
        if (!dp.get(idx).contains(w)) {
            if (dfw(idx - 1, w + weight[idx]) && dfw(idx - 1, w - weight[idx])) {
                dp.get(idx).add(w);
            } else {
                return false;
            }
        }
        return true;
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}