#!/bin/python3

import sys
def howManyGames(p, d, m, s):
    # p = price of current game.
    g = 0
    while p > m and s >= p:
        g += 1
        s -= p
        p -= d
        
    if p < m:
        p = m
    if s >= p:
        g += int(s/p)
    
    return g

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)