import java.util.Arrays;
import java.util.Scanner;

public class No4 {
    public static void main (String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int W[] = new int[N];
        for (int i = 0; i < N; i++) W[i] = scan.nextInt();
        Arrays.sort(W);
        int left = W[N-1], right = W[N-2];
        for (int i = N-3; i >= 0; i--) {
            if (left > right) right += W[i];
            else left += W[i];
        }
        if (left == right) System.out.println("possible");
        else  System.out.println("impossible");
    }
}