import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int r = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();

        int dist = (int) Math.ceil(Math.sqrt(Math.pow(Math.abs(x2 - x1), 2) + Math.pow(Math.abs(y2 - y1), 2)) / (2 * r));

        System.out.println(dist);
    }
}