import java.util.Scanner;
class C{
	static Scanner s=new Scanner(System.in);
	static long d,l,c,r;
	public static void main(String[] args){
		d=s.nextLong();
		l=s.nextLong();
		c=s.nextLong();
		r=s.nextLong();
		if(d==0&&!kadomatsued()){
			System.out.println(-1);
		}else if(kadomatsued()){
			System.out.println(0);
		}else{
			System.out.println(Math.min(Math.abs(l-c), Math.abs(r-c))/d+1);
		}
	}
	static boolean kadomatsued(){
		return (c>l&&c>r)||(c<l&&c<r);
	}
}