#include <bits/stdc++.h>
int a[210], c[210], n;
using namespace std;
inline int read() {
  int f = 1, x = 0;
  char ch;
  do {
    ch = getchar();
    if (ch == '-') f = -1;
  } while (ch < '0' || ch > '9');
  do {
    x = x * 10 + ch - '0';
    ch = getchar();
  } while (ch >= '0' && ch <= '9');
  return f * x;
}
int main() {
  n = read();
  for (int i = 1; i <= n; i++) a[i] = read();
  for (int i = 1; i <= n; i++) c[a[i]]++;
  sort(a + 1, a + n + 1);
  if (a[n] & 1) {
    for (int i = a[n] / 2 + 1; i <= a[n]; i++)
      if (c[i] < 2) return puts("Impossible"), 0;
    if (a[1] <= a[n] / 2 || (n > 2 && a[3] == a[n] / 2 + 1))
      puts("Impossible");
    else
      puts("Possible");
  } else {
    if (c[a[n] / 2] < 1) return puts("Impossible"), 0;
    for (int i = a[n] / 2 + 1; i <= a[n]; i++)
      if (c[i] < 2) return puts("Impossible"), 0;
    if (a[1] < a[n] / 2 || a[2] == a[n] / 2)
      puts("Impossible");
    else
      puts("Possible");
  }
}
