#!/bin/python

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    current_price = p
    num_games = 0
    while s >= current_price:
        # purchase game
        s -= current_price
        num_games += 1
        
        if current_price > m:
            current_price = current_price - d if (current_price - d) >= m else m
    
    return num_games

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