#include <iostream>
#include <vector>
#include <stack>
#include <algorithm>

using namespace std;

bool chk( vector<int> w, int i, int half );

int main()
{
	int N;
	cin >> N;

	vector<int> W(N);
	for(int i = 0 ; i < N; i++ ){
		cin  >> W[i];
	}
	sort( W.begin(), W.end() );

	int half = 0;
	for( auto x: W ) {
		half += x;
	}

	if( half%2 == 1 )  {
		cout << "impossible" << endl;
		return 0;
	}
	half = half / 2;


	if( chk( W, 0, half ) ) {
		cout << "possible" << endl;
	}
	else {
		cout << "impossible" << endl;
	}

	return 0;
}
bool chk( vector<int> w, int i, int half )
{
	if( i >= w.size() ) {
		return false;
	}
	if( w[i] == half ) {
		return true;
	}
	if( w[i] < half ) {
		bool tmp = chk( w, i+1, half - w[i] );
		if( tmp ) {
			return true;
		}
		if( i <= 0 ) {
			return false;
		}
		//return chk( w, i-1, half+w[i] );
		//return chk( w, i+2, half );
		return false;
		
	}
	if( w[i] > half ) {
		return false;
	}

	return false;
}