#include <iostream>
using namespace std;
int main(){
  int n;
  cin >> n;
  int i=1;
  while(i*i<=n) i++;
  cout << (i-1)*(i-1) << "\n";
  return 0;
}

#include <iostream>
#include <vector>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <iomanip>
#include <numeric>
#include <queue>
#include <cmath>
using namespace std;


int main() {
    int n;
    cin >> n;
    n = pow(n, 0.5);
    cout << n * n << endl;
}


