#!/bin/python3

import sys
def price(p, d, m, games):
    prices = p - d * games
    if prices < m:
        return m
    else:
        return prices

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

    

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)