#include <iostream>
using namespace std;

int main(void){
	int n,i,t,v,all = 0;
	cin >> n;
	int w[n];
	for(i = 0;i < n;i++){
		cin >> w[i];
		all += w[i];
	}
	if(all % 2 != 0){
		cout << "impossible" << endl;
		return 0;
	}
	for(i = 0;i < n;i++){
		for(t = i+1;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;i++){
		v = w[i];
		for(t = i + 1;t < n;t++){
			cout << "all:" << all << ",i:" << i << ",t:" << t << endl;
			if(all >= v + w[t]){
				v += w[t];
				if(all == v){
					cout << "possible" << endl;	
					return 0;	
				}
				cout << "v:" << v << ",i:" << i << ",t:" << t << endl;
			} else {
				v -= w[t-1];
				continue;
			}
		}		
	}
	cout << "impossible" << endl;
}