import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Scanner;
public class scratch_16{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
            int r= sc.nextInt();
            int x1= sc.nextInt();
            int y1= sc.nextInt();
            long ans=0;
            int x2= sc.nextInt();
            int y2= sc.nextInt();
            long h= (long)(x1-x2)*(long)(x1-x2);
            long g= (long)(y1-y2)*(long)(y1-y2);
            double d= Math.sqrt(h+g);
            double p= (d-2*r)/(2*r);


        System.out.println((int)(Math.ceil(p))+1);










    }}