
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner obj = new Scanner(System.in);
		int r=obj.nextInt(),x1=obj.nextInt(),y1=obj.nextInt(),x2=obj.nextInt(),y2=obj.nextInt();
		double dist =  (Math.pow((x1-x2), 2)+Math.pow((y1-y2), 2));
		dist=Math.sqrt(dist);
		System.out.println((int)Math.ceil(dist/(r*2)));
	}

}
