
import java.util.*;

public class Expert {

    public static Scanner in = new Scanner(System.in);

    public static double getDist(double x1, double y1, double x2, double y2) {
        double dist = Math.sqrt((Math.pow(Math.abs(x1 - x2), 2)) + (Math.pow(Math.abs(y1 - y2), 2)));
        return dist;
    }

    public static void main(String[] args) {
        double r = in.nextInt();
        double x = in.nextInt();
        double y = in.nextInt();
        double x1 = in.nextInt();
        double y1 = in.nextInt();
        if (x == x1 && y == y1) {
            System.out.println("0");
        } else {
            int ans = (int) Math.ceil(getDist(x, y, x1, y1) / (2 * r));
            System.out.println(ans);
        }
    }

}
