#include <bits/stdc++.h>
using namespace std;
#define _GLIBCXX_DEBUG
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define ll long long
#define P pair<ll,ll>
#define all(v) (v).begin(),(v).end()

const ll mod = 1e9+7;
const ll INF = 1e18;
const double pi = acos(-1.0);

int main(void)
{
    ll n; cin>>n;
    ll ans=1;
    for(ll i=1;i<=n;i++){
        if(i*i<=n) ans=max(ans,i*i);
    }
    cout<<ans<<endl;
    return 0;
}
#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define repI(i, d, n) for (int i = (d); i < (n); ++i)
#define reps1(i, n) for (int i = 1; i < (n); ++i)
using namespace std;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using ll = long long;
using P = pair<int, int>;
using Pl = pair<ll, ll>;
using M = map<int, int>;
using Ml = map<ll, ll>;
ll const INF = 1ll<<61;
double pi = 3.141592653589793238;

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

  cout << ll(sqrt(n)) * ll(sqrt(n)) << endl;

  return 0;
}
