#!/bin/python3

import sys

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

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)