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 (Clang 3.8.0) (judge verdict: Accepted)

#include <algorithm>
#include <cmath>
#include <iostream>
#include <iterator>
#include <map>
#include <set>
#include <string>
#include <vector>

using namespace std;
using ull = unsigned long long;

int main() {
    ull N;
    cin >> N;

    ull ans = 1;
    for (ull i = 1; i * i <= N; ++i) {
        ans = i * i;
    }
    cout << ans << endl;
}