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)

#region using directives
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using static System.Console;
using static System.Convert;
#endregion

namespace for_contests
{
    class Program
    {
        static void Main()
        {
            long n = ToInt64(ReadLine());
            long i = 1;
            long max = 1;
            while(true)
            {
                long t = i;
                t = t * t;
                if (t <= n)
                    max = t;
                else
                    break;
                i++;
            }
            WriteLine(max);
        }
    }
}