import java.util.Scanner;
public class amrAndPins {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        
        int r = sc.nextInt();
        double x = sc.nextDouble();
        double y = sc.nextDouble();
        double x2 = sc.nextDouble();
        double y2 = sc.nextDouble();
        double dist = Math.sqrt(Math.pow((x - x2), 2) + Math.pow((y - y2), 2));
        
        double resposta = dist / (2*r);
        double comp = resposta * r * 2;
       if(resposta != comp) {
           resposta++;
       }
       
       System.out.println(Integer.toString((int) resposta));
    }
}

  	 	 	   	 	 	 	 	 	 						 		