import java.util.*;
public class CF{ 
    public static void main(String arg[]){
        Scanner sc =  new Scanner(System.in);
        long r = sc.nextLong(), x = sc.nextLong(), y = sc.nextLong(), xd = sc.nextLong(), yd = sc.nextLong();
        long z = (x-xd)*(x-xd) + (y-yd)*(y-yd);
        long dist = (long)Math.sqrt(z);
        long ans = 0;
        if((dist*dist)==z){
            ans = dist/(2*r);
            if(dist%(2*r)!=0) ans++;
        }else{
            ans = (dist/(2*r)) + 1;
        }
        System.out.println(ans);
    }
}