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>
using namespace std;
#define rep(i,n) for (int (i)=0;(i)<(n);i++)
#define INF 1001001001
#define LLINF 1001001001001001001
#define MOD 1000000007
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; }
#define ALL(v) v.begin(), v.end()
typedef long long ll;



int main(){

ll n;cin >> n;
ll tem=0;
for(ll i=0;i<n;i++){
    if(i*i>n)break;
    else {
        tem=max(tem,i*i);
    }
}
cout << tem << endl;
return 0;
}