import java.util.Scanner;

public class No4 {
    public static boolean check (int half, int[] W, int i, boolean b) {
        int tmp;
        i--;
        for (; i >= 0; i--) {
            if (b) break;
            tmp = half - W[i];
            if (tmp >= 0) {
                if (tmp == 0) b = true;
                else b = check(tmp, W, i, b);
            }
        }
        return b;
    }
    public static void main (String[] args) {
        Scanner scan = new Scanner(System.in);
        int N = scan.nextInt();
        int W[] = new int[N];
        int sum = 0; int half;
        boolean b = false;
        for (int i = 0; i < N; i++) {
            W[i] = scan.nextInt();
            sum += W[i];
        }
        //合計が奇数なら２等分することはできない
        if (sum % 2 != 0) {
            System.out.println("impossible");
            System.exit(0);
        }
        half = sum/2;
        if (check(half, W, N, b)) System.out.println("possible");
        else System.out.println("impossible");
    }
}