#include<bits/stdc++.h>
using namespace std;
int main(){
  int n;
  cin>>n;
  int a;
  for(int i=0;i*i<=n;i++)
    a=i*i;
  cout<<a<<endl;
}
/** author: __nishad__ **/
//#pragma GCC optimize(2)
//#pragma GCC optimize(3, "Ofast", "inline")
#include<bits/stdc++.h>
using namespace std;


typedef long long ll ;
typedef vector<ll> vll ;

#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define all(v) (v).begin(),(v).end()
#define precision(k) cout<<setprecision(k)<<fixed;
#define loop(i,a,b) for(ll i=(a);i<=(b);++i)
#define minv(v) *min_element(all(v))
#define maxv(v) *max_element(all(v))
#define getpos(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define unq(v) sort(all(v)),(v).erase(unique((v).begin(),(v).end()),(v).end())
#define pb push_back
#define mp make_pair
#define pi 3.14159265358979323
#define endl "\n"

int main()
{
    IOS;

    ll n, max=0;
    cin>>n;
    int i;

    for(i=n; i>0; i--){
        if(sqrt(i) == int(sqrt(i))){
            max = i;
            cout<<max;
            return 0;
        }
    }




}



























