Problem:
Score : 200 points

Problem Statement

Find the largest square number not exceeding N. Here, a square number is an integer that can be represented as the square of an integer.

Constraints

1 \leq N \leq 10^9

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the largest square number not exceeding N.

Sample Input 1

10

Sample Output 1

9

10 is not square, but 9 = 3 × 3 is. Thus, we print 9.

Sample Input 2

81

Sample Output 2

81

Sample Input 3

271828182

Sample Output 3

271821169

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

/*
これを入れて実行
g++ code.cpp
./a.out
 */

#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <algorithm>
#include <utility>
#include <set>
#include <map>
#include <cmath>
#include <tuple>
#include <iomanip>

using namespace std;
typedef long long ll;
typedef long double ld;

int dy4[4] = {-1, 0, +1, 0};
int dx4[4] = {0, +1, 0, -1};
int dy8[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dx8[8] = {0, 1, 1, 1, 0, -1, -1, -1};

const long long INF = 1LL << 60;
const ll MOD = 1e9 + 7;

bool greaterSecond(const pair<int, int>& f, const pair<int, int>& s){
    return f.second > s.second;
}

int gcd(int a, int b){
	if (b == 0)return a;
	return gcd(b, a % b);
}

ll nCm(ll n, ll m){
    if(m == 0 || m == n){
        return 1;
    } else if(m == 1){
        return n;
    }
    return (nCm(n - 1, m) + nCm(n - 1, m - 1));
}

//-----------------------ここから-----------

int main(void){
    ll n;
    cin >> n;
    
    ll ans = 0;

    for(ll i = 1; i < 100001; i++){
        if(n < i * i){
            cout << (i - 1) * (i - 1) << endl;
            return 0;
        }
    }

}