/* -*- coding: utf-8 -*-
 *
 * 4.cc: No.4 おもりと天秤 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100;

/* typedef */

/* global variables */

int n, as[MAX_N];

/* subroutines */

void rec(int h, int u) {
  if (h == 0) {
    puts("possible");
    exit(0);
  }
  if (u >= n) return;

  if (h >= as[u]) rec(h - as[u], u + 1);
  rec(h, u + 1);
}

/* main */

int main() {
  cin >> n;

  int sum = 0;
  for (int i = 0; i < n; i++) {
    cin >> as[i];
    sum += as[i];
  }

  if (sum & 1) {
    puts("impossible");
    return 0;
  }

  sort(as, as + n, greater<int>());

  int h = sum / 2 - as[0];
  if (h < 0) {
    puts("impossible");
    return 0;
  }

  rec(h, 1);

  puts("impossible");
  return 0;
}