#!/bin/python

import sys

def howManyGames(p, d, m, s):
    cash_left = s
    price = p
    games = 0
    while cash_left - price >= 0:
        cash_left -= price
        games += 1
        if price - d >= m:
            price -= d
        else:
            price = m
    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