#!/bin/python3

import sys

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

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)