package yukicoder;

import java.util.ArrayList;
import java.util.Scanner;

public class N4 {
	private int n;
	private int[] bobs;
	
	public static void main(String[] args){
		N4 n4 = new N4();
	}

	N4(){
		Scanner sc = new Scanner(System.in);
		this.n = sc.nextInt();
		this.bobs = new int[n];
		int[][] visited = new int[n][n];
		
		for(int i = 0;i < n;++i){
			bobs[i] = sc.nextInt();
		}
		
		if(!this.solve(0, 0, 0, visited)){
			System.out.println("impossible");
		}else{
			System.out.println("possible");
		}
	}
	
	//めう
	private boolean solve(int k, int left, int right, int[][] visited) {
		int b = bobs[k];
		if(k < n - 1){
			boolean alpha = solve(k + 1, left + b, right, visited);
			boolean beta = solve(k + 1, left, right + b, visited);
			return alpha | beta;
		}else{
			if(left + b == right){
				return true;
			}else if(right + b == left){
				return true;
			}else{
				return false;
			}
		}
	}
}