package main

import (
	"fmt"
)

func main() {
	solve281()
}

func solve281() {
	var d, a, b, c int
	fmt.Scan(&d, &a, &b, &c)
	/// d==0 のときなにもできない
	if d == 0 {
		if isKadomatsu(a,b,c){
			fmt.Println("0")
		} else {
			fmt.Println("-1")
		}
		return
	}

	var cnt1, cnt2 int
	b1 := b
	if a == 0 || c == 0 {
		cnt1 = -1
	} else {
		if d > 0 {
			foo := ((b - min(a, c)) / d) - 1
			if foo > 0 {
				cnt1 += foo
				b1 = max(0, b1-d*foo)
			}
		}
		for a <= b1 || c <= b1 {
			cnt1++
			b1 = max(0, b1-d)
			if b1 == 0 {
				break
			}
		}
		ax := a
		if a==c&&cnt1>=0{
			ax=max(0, ax-d)
			cnt1++
		}
		if isKadomatsu(ax, b1, c)==false{
			cnt1=-1
		}
	}

	if b == 0 {
		cnt2 = -1
	} else {
		a1 := a
		if d > 0 {
			bar := ((a - b) / d) - 1
			if bar > 0 {
				cnt2 = bar
				a1 = max(0, a1-d*bar)
			}
		}
		for a1 >= b {
			cnt2++
			a1 = max(0, a1-d)
			if a1 == 0 {
				break
			}
		}
		c1 := c
		if d > 0 {
			foobar := ((c - b) / d) - 1
			if foobar > 0 {
				cnt2 += foobar
				c1 = max(0, c1-d*foobar)
			}
		}
		for c1 >= b {
			cnt2++
			c1 = max(0, c1-d)
			if c1 == 0 {
				break
			}
		}
		if a1 == c1 {
			cnt2 = -1
		}
		ax := a
		if a==c&&cnt2>=0{
			ax=max(0, ax-d)
			cnt2++
		}
		if isKadomatsu(ax, b, c1)==false{
			cnt2=-1
		}
	}

	//fmt.Println(cnt1, cnt2)
	if cnt1 == -1 && cnt2 == -1 {
		fmt.Println("-1")
	} else if cnt1 == -1 {
		fmt.Println(cnt2)
	} else if cnt2 == -1 {
		fmt.Println(cnt1)
	} else {
		fmt.Println(min(cnt1, cnt2))
	}
//	fmt.Println(cnt1, cnt2)
//	fmt.Println(a,b1,c)
}

func isKadomatsu(a, b, c int)bool{
	if a<b&&b>c&&a!=c{
		return true
	}else if a>b&&b<c&&a!=c{
		return true
	}
	return false
}

func max(a, b int) int {
	if a < b {
		a = b
	}
	return a
}

func min(a, b int) int {
	if a > b {
		a = b
	}
	return a
}