#!/bin/python3

import sys

def howManyGames(p, d, m, s):
    # Return the number of games you can buy
    curPrice = p
    res = 0
    while True:
        if s >= curPrice:
            #print("price: %s" % curPrice)
            res += 1
            s -= curPrice
        else:
            break
        if curPrice > m:
            curPrice = max(curPrice - d, m)
    return res
        

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)