#include <bits/stdc++.h>
using namespace std;
long long gcd(long long n1, long long n2) {
  if (n1 % n2 == 0) return n2;
  return gcd(n2, n1 % n2);
}
long long powmod(long long base, long long exponent) {
  long long ans = 1;
  while (exponent) {
    if (exponent & 1) ans = (ans * base) % 1000000007;
    base = (base * base) % 1000000007;
    exponent /= 2;
  }
  return ans;
}
bool isPerfectSquare(long long n) {
  long long squareRootN = (long long)round((sqrt(n)));
  if (squareRootN * squareRootN == n) {
    return true;
  } else {
    return false;
  }
}
int main() {
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  for (int i = n - 1; i >= 0; i--) {
    if (isPerfectSquare(a[i]) == false) {
      cout << a[i] << '\n';
      break;
    }
  }
}
