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)

#include <stdio.h>
#include <iostream>
#include <iomanip>
#include <vector>
#include <cstdlib>
#include <cmath>
#include <numeric>
#include <algorithm>
#include <sstream>
#include <string>
#include <map>
#include <set>
using namespace std;

#define rep(i, n) for (int i=0; i<int(n); i++)


int main() {
	int64_t N;
	cin >> N;
	int64_t ans = 1;
	for(int i=1; i<N; i++) {
		if (i*i<=N) ans = i*i;
		else {
			cout << ans << endl;
			return 0;
		}
	}
	cout << ans << endl;
}