#include <bits/stdc++.h>
#define rep(i, f, n) for (ll i = (f); i < (ll)(n); i++)
#define repe(i, f, n) for (ll i = (f); i <= (ll)(n); i++)
using namespace std;
using ll = long long;
using pint = pair<int, int>;

int main() {
  int N;
  cin >> N;
  for (int i = N; i > 0; i--) {
    double a = sqrt(i);
    if (ceil(a) == floor(a)) {
      cout << i << endl;
      return 0;
    }
  }

  return 0;
}

#include<bits/stdc++.h>
using namespace std;
///Welcome to Nasif's Code
#define bug printf("bug\n");
#define bug2(var) cout<<#var<<" "<<var<<endl;
#define co(q) cout<<q<<endl;
#define all(q) (q).begin(),(q).end()
typedef long long int ll;
typedef unsigned long long int ull;
const int MOD = (int)1e9+7;
const int MAX = 1e6;
#define pi acos(-1)
#define inf 1000000000000000LL
#define FastRead    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int main()
{
    FastRead
    //freopen("output.txt", "w", stdout);
    ll n,m;
    cin>>n;
    m=sqrt(n);
    cout<<m*m<<endl;



    return 0;
}
