#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
using namespace std;

using ll = long long;

const int INF = 1001001001;
const ll INF_LL = 1001001001001001001LL;

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

  int ans = -1;
  for(int i = 1;i*i<=n;i++)
    ans = max(ans,i*i);

  cout << ans << endl;
  
  return 0;
}

#include<iostream>
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pi;

#define F first
#define S second
#define PB push_back
#define MP make_pair
#define what_is(x) cerr << #x << " is " << x << endl;
#define MT make_tuple
#define eb emplace_back
#define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))

#define REP(i,a,b) for (int i = a; i <= b; i++)
#define FOR(i,n) for (int i=0;i < n ; i++)
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }

void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
	cerr << *it << " = " << a << endl;
	err(++it, args...);
}

int main(){
	ll n;
	ll i;
	cin >> n;
	i=0;
	while((i+1)*(i+1)<=n) i++;
	cout << i*i;

	return 0;
}