#!/bin/python

import sys

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