

import java.util.Scanner;

public class AmrAndPins {

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

}
