import java.util.Scanner;

public class B507 {

	public static void main(String[] args) {
		Scanner sc= new Scanner(System.in);
		int r=sc.nextInt();
		double x=sc.nextInt(), y=sc.nextInt(),x1=sc.nextInt(), y1=sc.nextInt();
		double a=x1-x;
		double b=y1-y;
		double d= Math.sqrt((Math.pow(a, 2)+Math.pow(b, 2)));
		System.out.println((int)Math.ceil(d/(2*r)));
	}
}
