using System.Diagnostics;
using System.Numerics;

public class Program
{
    public static void Main()
    {

        //BigInteger num = BigInteger.Parse(Console.ReadLine() ?? string.Empty);
        //int num = int.Parse(Console.ReadLine() ?? string.Empty);
        string[] moji = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string str = Console.ReadLine() ?? string.Empty;


        int reef = int.Parse(moji[0]);
        int fall = int.Parse(moji[1]);
        int start = int.Parse(moji[2]);
        int end = int.Parse(moji[3]);

        int month = 1;
        int monthCount = 0;
        while(reef > 0)
        {
            if(month >=start && month <= start+end-1)
            {
                reef -= fall * 2;
            }
            else
            {
                reef -= fall;
            }
            monthCount++;
            month++;
            if(month ==13)
            {
                month = 1;
            }
        }
        Console.WriteLine(monthCount);

    }
}