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# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections;
using System.Linq;


public class ABC077_Rotation
{
	public static void Main()
	{
		double N = double.Parse(Console.ReadLine());
        bool b = false;
        double heihou;
        while(b == false){
            heihou = Math.Sqrt(N);
            if(heihou - Math.Floor(heihou) == 0){
                b = true;
                break;
            }
            N--; 
        }
        Console.WriteLine(N);
	}
}