#!/bin/python3

import sys

p, d, m, s = input().strip().split(' ')
p, d, m, s = [int(p), int(d), int(m), int(s)]
cost=p
item=0
sale=p
while(cost<=s):
    sale-=d
    item+=1 
    if(sale<=m):
        cost+=m
    else:
        cost+=sale
print(item)