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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#define maxn 1000000000

int main()
{
    long long n;
    while(~scanf("%lld",&n))
    {
    long long i;
       for(i=n;i>=sqrt(n);i--)
       {
           int a=sqrt(i);
           if(a*a==i)
           {
               printf("%lld\n",i);
               break;
           }
       }
    }
    return 0;
}