#include <bits/stdc++.h>
using namespace std;
inline int getInt() {
  int res(0);
  char c = getchar();
  while (c < '0') c = getchar();
  while (c >= '0') {
    res = res * 10 + (c - '0');
    c = getchar();
  }
  return res;
}
inline int fastpo(int x, int n, int mod) {
  int res(1);
  while (n) {
    if (n & 1) {
      res = res * (long long)x % mod;
    }
    x = x * (long long)x % mod;
    n /= 2;
  }
  return res;
}
const int N = 300033;
const int LOG = 20;
const int mod = 1e9 + 7;
const int inf = 1e9 + 7;
bool f[1111111];
int main() {
  for (int i(0); i <= 1000; i++) f[i * i] = true;
  int n;
  scanf("%d", &n);
  int ans = -inf;
  for (int i(1); i <= n; i++) {
    int x;
    scanf("%d", &x);
    if (x >= 0 && f[x]) {
    } else {
      ans = max(ans, x);
    }
  }
  cout << ans << endl;
}
