using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("How many people will be in the party?");

        int Pnum = int.Parse(Console.ReadLine());

        int Pnum1 = Pnum/13;

        int Pnum2 = Pnum1+1;

        if (Pnum%13 == 0)

            Console.WriteLine("you'll need " + Pnum1 + " pizza trays");

        else

        {

            Console.WriteLine("you'll need " + Pnum2 + " pizza trays");

        }

    }

}