#!/bin/python

import sys

def howManyGames(p, d, m, s):
    c = 0
    while s > 0:
        s -= p
        p -= d
        if p < m:
            p = m
        if s >= 0:
            c += 1
    return c

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