#!/bin/python

import sys

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