using System;

public class Program

{

  public static void Main ()

  {

    int god=2000, br = 0;

    double ton = 20, s = 20;

      while (true)

      {

          god += 1;

            if (god % 2 == 0)

            {

                ton += ton * 0.2;

                if (ton > 50 && br == 0)

                {

                    Console.WriteLine(god);

                    br++;

                }   

            }

          s += ton;

            if (s > 900)

            {

                Console.WriteLine(god);

                break;

            }         

      }

  }

}