using System;
using static System.Console;
using static System.Math;

public class Hello{
    public static void Main(){
//        int kazu = int.Parse(ReadLine());
        string[] temp = ReadLine().Split(' ');
        int a = int.Parse(temp[0]);
        int b = int.Parse(temp[1]);
        int p = int.Parse(temp[2]);
        int q = int.Parse(temp[3]);
        
        int m2 = 1;
        for(int i=0;i<b;i++){
            m2*=2;
            if(m2>=a){
                break;
            }
        }
        
        int ans=0;
        int tsuki =0;
        while(a>0){
            tsuki++;
            int k = tsuki%12;
            if(k==0){
                k=12;
            }
                if(p <= k && k <= p+q-1){
                    a-=m2;
                }else{
                    a-=b;
                }
                ans=tsuki;
                if(a<=0){
                    break;
                }
        }
        WriteLine(ans);
    }
}