package main

import "fmt"

func main() {
	var l int
	line := make([]int, 4)
	for i := 0; i < 4; i++ {
		fmt.Scan(&l)
		line = append(line[:i], l)
	}
	p := line[0]
	d := line[1]
	m := line[2]
	s := line[3]
	var total, c int
	po := p
	for total <= s {
		if c == 0 {
			total = p
			c++
		} else {
			price := po - d
			if price <= m {
				total += m
				c++
			} else {
				total += price
				c++
			}
			po = price
		}
	}
	game := c - 1
	fmt.Println(game)
}