import java.util.Scanner;

public class EX510A {

    public static void main(String[] args) {
        // TODO Auto-generated method stub

        Scanner in = new Scanner(System.in);
        int r = in.nextInt();
        int x = in.nextInt();
        int y = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();

        double dist = Math.sqrt(Math.pow(x1 - x, 2) + Math.pow(y1 - y, 2));
        double res = dist / (r * 2f);
        System.out.println((int) Math.ceil(res));
    }
}
