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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PracticeOOP
{
    class Program
    {
        static void Main(string[] args)
        {

            try
            {
                long N = Convert.ToInt64(Console.ReadLine());
                long[] array = new long[N];

                for (long i = 0; i < N; i++)
                {
                    array[i] = Convert.ToInt64(Math.Sqrt(i + 1));
                }

                long max = array[0];
                for (long i = 0; i < N; i++)
                    if (array[i] > max)
                        max = array[i];

                Console.WriteLine(Math.Pow(max, 2));
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }


            
        }
        
        

    }//end program class


}