import java.util.Scanner;

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