#include<iostream>
#include<stdio.h>
#include<string>
#include<vector>
#include<sstream>
using namespace std;

void dfs(int index, int right, int left, int n, vector<int> w){
	if (index == n){
		if (right == left){
			cout << "possible" << endl;
			exit(0);
		}return;
	}

	dfs(index + 1, right + w[index], left, n, w);
	dfs(index + 1, right, left + w[index], n, w);

	return;
}

int main(){
	int n;
	cin >> n;
	vector<int> w;
	int temp;
	for (int i = 0; i < n; i++){
		cin >> temp;
		w.push_back(temp);
	}
	dfs(1, w[0], 0, n, w);
	dfs(1, 0, w[0], n, w);
	cout << "impossible" << endl;
	return 0;
}