import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {


	   static int howManyGames(int p, int d, int m, int s) {
		   int total=0;
		   int count=0;
	        for(int i=p ; ; ){
	        	
	        		total+=i;
	        		if(total>s)break;
	        		if(i-d<m) i=m;
	        		else i=i-d;
	        		count++;
	   
	        }
	        return count;
	    }

	    public static void main(String[] args) {
	        Scanner in = new Scanner(System.in);
	        int p = in.nextInt();
	        int d = in.nextInt();
	        int m = in.nextInt();
	        int s = in.nextInt();
	        int answer = howManyGames(p, d, m, s);
	        System.out.println(answer);
	        in.close();
	    }
	}