#!/bin/python3

import sys
import math

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