#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    c=0
    while(s>=0):
      s-=p
      if p>m:
            p-=d
      if p<=m:
        p=m
      c+=1;
    return c-1
if __name__ == "__main__":
    p, d, m, s = input().strip().split(' ')
    p, d, m, s = [int(p), int(d), int(m), int(s)]
    answer = howManyGames(p, d, m, s)
    print(answer)