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;
class p
{
  static void Main()
  {
    int N = int.Parse(Console.ReadLine());
    for (int i = N; 0 < i; i--) {
      if (Math.Sqrt(i) % 1 == 0.0) {
        Console.WriteLine(i);
        return;
      }
    }
  }
}