import java.util.Scanner;


public class AmrAndPins {

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

        double distance = Math.sqrt((x2-x1)*(x2-x1) + (y2-y1)*(y2-y1));
        System.out.println((int)Math.ceil(distance*1.0/(2*r)));
        
    }

}
