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++ (GCC 9.2.1) (judge verdict: Accepted)

/**
*    created: 03.07.2020 18:33:51
**/
#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
// #include <boost/multiprecision/cpp_int.hpp>
// using bint = boost::multiprecision::cpp_int;
using namespace std;
#define int long long
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep2(i, s, n) for (int i = (s); i < (int)(n); i++)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define pcnt(bit) __builtin_popcountll(bit)
template<class T> bool chmax(T &a, const T &b) {if (a < b) {a = b; return 1;} return 0;}
template<class T> bool chmin(T &a, const T &b) {if (b < a) {a = b; return 1;} return 0;}
const long double pi = acos(-1.0);
const int INF = 1LL << 60;
const int MOD = 1000000007;
// const int MOD = 998244353;

signed main() {

    cin.tie(0);
    ios_base::sync_with_stdio(false);

    int n;
    cin >> n;
    rep2(i,1,100001) {
        if (i*i <= n && n < (i+1)*(i+1)) {
            cout << i*i << endl;
            return 0;
        }
    }
    return 0;
}