import java.util.Scanner;

public class AmrAndPins {
    public static void main(String[] args) {
         Scanner in = new Scanner(System.in);
       long r=in.nextInt();
       long a=in.nextInt();
       long b=in.nextInt();
       long c=in.nextInt();
       long d=in.nextInt();
       double z=Math.sqrt(Math.pow(c-a, 2)+Math.pow(d-b, 2));
        System.out.println((int)Math.ceil((z/(2*r))));
      
    }
    
}
