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 <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
#define krep(i,k,n,m) for(int i=k;i<n;i+=m)
#define erep(i,k,n) for(int i=k;i<n;i++)
//最大公約数
int gcd(int s,int b){
    if(b==0)return s;
    return gcd(b,s%b);
}
signed main() {
    int n;
    cin>>n;
    for(int i=n;i>=1;i--){
        if(i*i<=n){
            cout<<i*i<<endl;
            break;
        }
    }
}