#include <iostream>
using namespace std;

int main(void){
	int n,i,all = 0;
	cin >> n;
	int w[n];
	for(i = 0;i < n;i++){
		cin >> w[i];
		all += w[i];
	}
	for(i = 0;i < n;i++){
		for(int t = i;t < n;t++){
			if(w[i] > w[t]){
				int z = w[t];
				w[t] = w[i];
				w[i] = z;
			}
		}
	}
	for(all /= 2,i = 0;i < n/2;i++){
		all -= w[i] + w[n-i];
		if(all == 0){
			cout << "possible" << endl;	
			break;
		}
		if(all < 0){
			cout << "impossible" << endl;
			break;	
		}
	}
}