#include <bits/stdc++.h>
using namespace std;
int n, a[105], cnt[105];
int main() {
  scanf("%d", &n);
  for (int i = (1); i <= (n); i++) scanf("%d", &a[i]), cnt[a[i]]++;
  sort(&a[1], &a[n + 1]);
  for (int i = (a[1] + 1); i <= (a[n]); i++)
    if (cnt[i] < 2) return puts("Impossible"), 0;
  if ((cnt[a[1]] == 2) != (a[n] & 1)) return puts("Impossible"), 0;
  puts("Possible");
  return 0;
}
