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.Linq;

public static class Prg{
    public static Scanner sc = new Scanner();
    public static void Main(){
        var n = sc.NextDouble();
        var r = (int)Math.Sqrt(n);
        Console.WriteLine(r);
    }
}

public static class Extension{
    public static IEnumerable<int> To(this int from, int to){
        return Enumerable.Range(from, to);
    }

    public static void Times(this int times, Action<int> action){
        0.To(times).ToList().ForEach(x => action(x));
    }
}
public class Scanner{
    private string line;
    private string[] token;
    private int cursole = 0;
    
    public string ReadLine(){
        line = Console.ReadLine();
        token = line.Split(' ');
        cursole = 0;
        return line;    
    }
    
    public string Next(){
        if(token == null) ReadLine();
        if(token.Length <= cursole) ReadLine();
        var ret = token[cursole];
        ++cursole;
        return ret;
    }

    public IEnumerable<double> NextDoubleList(){
        return NextList().Select(s => Double.Parse(s));
    }

    public int NextInt(){return Int32.Parse(Next());}
    
    public long NextLong(){return Int64.Parse(Next());}

    public double NextDouble(){return Double.Parse(Next());}

    public IEnumerable<string> NextList(){
        ReadLine();
        cursole = Int32.MaxValue;
        return token;
    }
    
    public IEnumerable<int> NextIntList(){
        return NextList().Select(s => Int32.Parse(s));
    }
}