#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n];
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  sort(arr, arr + n, greater<int>());
  for (int i = 0; i < n; i++) {
    double x = sqrt(arr[i]);
    if (floor(x) != ceil(x)) {
      cout << arr[i] << endl;
      break;
    }
  }
  return 0;
}
