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

public class Main {
    static ArrayList<HashSet<Integer>> dp = new ArrayList<>();
    static int[] values;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        values = new int[n];
        for (int i = 0; i < n; i++) {
            values[i] = sc.nextInt();
            dp.add(new HashSet<>());
        }
        if (dfw(n - 1, 0)) {
            System.out.println("possible");
        } else {
            System.out.println("impossible");
        }
    }
    
    static boolean dfw(int idx, int v) {
        if (idx < 0) {
            return v == 0;
        }
        if (!dp.get(idx).contains(v)) {
            if (dfw(idx - 1, v + values[idx])) {
                return true;
            }
            if (dfw(idx - 1, Math.abs(v - values[idx]))) {
                return true;
            }
            dp.get(idx).add(v);
        }
        return false;
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    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 int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}