#include <bits/stdc++.h>
using namespace std;
int main(){
  int N;
  int W[101];
  int sum = 0;
  bool flag = false;
  cin >> N;
  for(int i = 1;i <= N;i++){
    cin >> W[i];
    sum += W[i];
  }
  if(!(sum & 1)){
    sum /= 2;
    bool dp[10001] = {0};
    dp[0] = true;
    for(int j = 0;j <= sum;j++){
      if(j - W[j] >= 0){
	dp[j] = dp[j - W[j]];
      }
      if(j == sum && dp[j] == true){flag = true;break;}
    }
  }
  if(flag)cout << "possible" << endl;
  else cout << "impossible" << endl;
  return 0;
}