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: Runtime Error)

using System;

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

           
          
            int N = Convert.ToInt32(Console.ReadLine());
            int[] array = new int[N];

            for (int i = 0; i < N; i++)
            {
                array[i] = Convert.ToInt32(Math.Sqrt(i + 1));
            }

            Array.Sort(array);
            Console.WriteLine(Math.Pow(array[array.Length-1], 2.0));

        }
        
        

    }//end program class


}