#!/usr/bin/env python

#Imports
import os
import sys
import math

def videoGame(listOfNums):
	#initializors
	costOfVG = listOfNums[0]
	dLess = listOfNums[1]
	minPrice = listOfNums[2]
	currentBalance = listOfNums[3]
	gamesBought = 0
	currentPrice = costOfVG

	while currentBalance >= currentPrice:
		gamesBought += 1
		currentBalance -= currentPrice
		if (currentPrice-dLess >= minPrice):
			currentPrice -= dLess
		else:
			currentPrice = minPrice
		#print str(currentBalance) + " " + str(gamesBought) + " " + str(currentPrice)


	return gamesBought
	

#numberOfClouds = int(raw_input().strip())
listOfNums = map(int, raw_input().strip().split(' '))

print videoGame(listOfNums)