#!/bin/python3

import sys

def howManyGames(p, d, m, s):
	count = 0
	while s >= p:
		count += 1
		s -= p
		if p >= m:
			p = max(m, p -d)

	return count

    # Return the number of games you can buy

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)