#include <bits/stdc++.h>

using namespace std;
 
using ll = long long;
using ull = unsigned long long;
using ldouble = long double;
 
const ll inf = 1ll << 60;
const ll mod = (ll)1e9 + 7;

#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define print(s) cout << s;
#define println(s) cout << s << endl;
#define printd(s) cout << fixed << setprecision(10) << s << endl;

ll res;

int main()
{
    ll n;
    cin >> n;

    ll res = 1;
    for (ll i = 1; ; i++)
    {
        
        if (i * i > n)
        {
            break;
        }
        res = i * i;
    }

    println(res)
}

#include <bits/stdc++.h>
using namespace std;
int main()
  {int N, i{}; cin >> N;
  while ((i + 1) * (i + 1) <= N) ++i;
  cout << i * i;}