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

using namespace std;

int main(){
  int n;
  vector<int> vec;
  cin >> n;
  int tmp;
  int sum;
  sum = 0;
  for(int i=0;i<n;i++){
    cin >> tmp;
    sum += tmp;
    vec.push_back(tmp);
  }
  
  if(sum % 2 == 1){
    cout << "impossible" << endl;
    return 0;
  }
  
  sort(vec.begin(), vec.end());
  int a = sum / 2;
  int b;
  b = 0;
  
  vector< vector<int> >  vecs;
  vector<int> side1;
  vector<int> side2;
  
  side1.push_back(0);//sum
  side1.push_back(1);//nextIndex
  side2.push_back(vec[1]);//sum
  side2.push_back(1);//nextIndex
  vecs.push_back(side1);
  vecs.push_back(side2);
  
  //覚えたての深さ優先探索を使う  
  while(vecs.size() > 0){
    vector<int> side3;
    side3 = vecs.back();
    vecs.pop_back();
    
    if(side3[0] == a){
      cout << "possible" << endl;
      return 0;
    }else if(side3[0] < a && side3[1] < n){
      int index = side3[1];
      side3[1]++;
      vecs.push_back(side3);
      side3[0] += vec[index];
      vecs.push_back(side3);
    }
  }
  cout << "impossible" << endl;
  return 0;
  
}