#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    nr_of_games = 0
    left_money = s
    actual_price = p
    while left_money > 0:
        if left_money >= actual_price:
            left_money = left_money - actual_price
            nr_of_games += 1
            actual_price = max(actual_price - d, m)
        else:
            return nr_of_games

    return nr_of_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