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 <iostream>
#include<stdio.h>
#include<math.h>
using namespace std;
long long n=100009;
long long a[1000001];
int main()
{
    long long m;
    for(int i=1;i<=n;i++)
    {
        a[i]=pow(i,2);
    }
    while(~scanf("%lld",&m))
    {
        int sum=0;
        for(int j=0;j<=n;j++)
        {
            if(a[j]<=m&&a[j+1]>m)
                printf("%lld\n",a[j]);
        }
    }
    return 0;
}