using System;
using System.Collections.Generic;
using System.Linq;

namespace StudyApp
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] inputs = Console.ReadLine().Split(' ');
            int initial = int.Parse(inputs[0]);
            int lost = int.Parse(inputs[1]);

            int current_month = 1;
            List<int> windy_month = GetWindyMonth(int.Parse(inputs[2]), int.Parse(inputs[3])).ToList();
            int month_num = 0;

            while (initial > 0)
            {
                if (windy_month.Contains(current_month))
                {
                    initial -= lost * 2;
                }
                else
                {
                    initial -= lost;
                }
                current_month = current_month == 12 ? 1 : current_month + 1;
                month_num++;
            }

            Console.WriteLine(month_num);
        }

        static IEnumerable<int> GetWindyMonth(int start_month, int months)
        {
            for (int i = 0; i < months; i++)
            {
                yield return start_month + i;
            }
        }
    }
}