#!/bin/python

import sys

def howManyGames(p, d, m, s):
  prices = [p]
  while prices[len(prices)-1]-d>m:
    prices.append(prices[len(prices)-1]-d)
  # print prices


  games=0
  index = 0
  while 1:
    if s-prices[games]>=0:
      s -= prices[games]
      games+=1
      # print s, prices
      prices.append(m)
    else:
      break
  return games

if __name__ == "__main__":
  p, d, m, s = raw_input().strip().split(' ')
  p, d, m, s = [int(p), int(d), int(m), int(s)]
  answer = howManyGames(p, d, m, s)
  print answer