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: Wrong Answer)

#include <bits/stdc++.h>
#define repl(i, l, r) for (int i = l; i < r; i++)
#define rep(i, n) repl(i, 0, n)
using namespace std;
using ll = long long;
using Graph = vector<vector<int>>;
using P = pair<int, int>;

int main()
{
    ll n;
    cin >> n;
    rep(i, n + 1) {
        if(i * i > n) {
            cout << (i - 1) * (i - 1) << endl;
            break;
        }
    }
    return 0;
}