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.Linq;
using System.Collections.Generic;
using System.IO;
 
public class Program
{
 
    public static void Main()
    {
        int N = int.Parse(Console.ReadLine());
        int sq = 0;
        int ans = 0;
        while (true)
        {
            sq = Convert.ToInt32(Math.Round(Math.Sqrt(N)));
            if (sq * sq == N) { ans = N; break; }
            N--;
        }
        Console.WriteLine(ans);
    }
 
}