import java.util.*;
public class circle{
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		int r=sc.nextInt();
		int x=sc.nextInt();
		int y=sc.nextInt();
		int x1=sc.nextInt();
		int y1=sc.nextInt();
		double d=Math.sqrt(((x1-x)*(x1-x))+((y1-y)*(y1-y)));
		int moves=(int)Math.ceil(d/(2*r));
		System.out.println(moves);



	}
}