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

public class OmoritoTenbin {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int N = s.nextInt(),total = 0;
		int[] W = new int[N+1];
		W[0] = 0;
		for(int i = 1;i <= N ;i++){
			W[i] = s.nextInt();
			total += W[i];
		}
		s.close();
		Arrays.sort(W);
		if(total % 2 == 1){
			System.out.println("impossible");
		}else{
			total /=2;
			int[][] way = new int[total+1][2];
			way[0][0] = 1;
			for(int i = 0;i <= total;i++){
				for(int j = 1;j <= N;j++){
					if(i-W[j] >= 0 &&way[i-W[j]][0] == 1 && way[i-W[j]][1] < j){
						way[i][0] = 1;
						way[i][1] = j;
						break;
					}
				}
				//System.out.println(i + "  " + way[i][0] + "  " + way[i][1]);
			}
			if(way[total][0] == 1){
				System.out.println("possible");
			}else{
				System.out.println("impossible");
			}
		}
	}
}