#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    price = p
    totprice = 0
    ngames = 0
    while totprice + price <= s:
        totprice += price
        ngames += 1
        if price - d < m:
            price = m
        else: price -= d
        # print(totprice, price, ngames)
    return ngames

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)