#include <bits/stdc++.h>

using namespace std;

int main() {
	int N,sum=0,ave=0;
	cin >> N;
	vector<int> W(N);

	vector<int> existance(10000);
	for (size_t i = 0; i < N; i++)
	{
		cin >> W.at(i);
		sum += W.at(i);
		existance.at(W.at(i)) = 1;

	}
	sort(W.begin(), W.end());
	if (sum%2||W.at(N-1)>sum/2)
	{
		cout << "impossible";
		return 0;
	}
	ave = sum / 2;
	for (size_t i = 0; i <= ave; i++)
	{
		for (size_t j = 0; j <i ; j++)
		{
			if (existance.at(j)*(existance.at(i-j)))
			{
				existance.at(i) = 1;
				break;
			}
		}
	}
	if (existance.at(ave)) cout << "possible";
	else cout << "impossible";
}