#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    outVal=1
    gameNum=0
    thisPrice=p
    keepGoing=True
    while (keepGoing):
        if s>=thisPrice:
            gameNum+=1
            s-=thisPrice
        else:
            keepGoing=False
        thisPrice-=d
        if thisPrice<m:
            thisPrice=m
    return gameNum
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)