#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    current_price = p
    count = 0
    while s - current_price >= 0:
        s -= current_price
        count += 1
        if current_price > m:
            current_price -= d
            if current_price < m:
                current_price = m
    return count

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)