import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main {
	
	public static boolean dfs(int deep, int N, int purpose, int current, boolean[] used){
		if(purpose == current){
			return true;
		}else if(purpose > current){
			return false;
		}else if(deep >= N){
			return false;
		}
		
		for(int i = deep; i < N; i++){
			if(!used[i]){
				used[i] = true;
				if(dfs(deep + 1, N, purpose, current, used)){
					return true;
				}
				used[i] = false;
			}
		}
		
		return false;
	}
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final int N = sc.nextInt();
		
		int[] arr = new int[N];
		for(int i = 0; i < N; i++){
			arr[i] = -sc.nextInt();
		}
		Arrays.sort(arr);
		for(int i = 0; i < N; i++){
			arr[i] = -arr[i];
		}
		
		final int purpose = Arrays.stream(arr).sum() / 2;
		
		System.out.println(dfs(0, N, purpose, 0, new boolean[N]) ? "possible" : "impossible");
		
		
	}
	
}