import java.util.*;
public class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        int r=sc.nextInt();
        int x0=sc.nextInt();
        int y0=sc.nextInt();
        int x1=sc.nextInt();
        int y1=sc.nextInt();
        
        double d=Math.sqrt((y0-y1)*(y0-y1)+(x0-x1)*(x0-x1));
        double ans=Math.ceil(d/(2*r));
        System.out.println(ans);
    }
}