import java.util.Scanner;

public class AmrAndPins {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int r = sc.nextInt();
		double x1 = sc.nextDouble(), y1 = sc.nextDouble(), x2 = sc.nextDouble(), y2 = sc.nextDouble();
		double dist = Math.sqrt((y2 - y1) * (y2 - y1) + (x2 - x1) * (x2 - x1));
		long k = (long) Math.floor(dist / (2 * r));
		if (2 * r * k != dist) {
			k++;
		}
		System.out.println(k);
	}

}
