import java.util.*;
public class sol
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        long r,x1,y1,x2,y2;
        r=sc.nextLong();
        x1=sc.nextLong();
        y1=sc.nextLong();
        x2=sc.nextLong();
        y2=sc.nextLong();
        if((x1==x2)&&(y1==y2))
        System.out.println("0");
        else
        {
        double dist=Math.sqrt(((x2-x1)*(x2-x1))+((y2-y1)*(y2-y1)))/r/2;
        long ans=(long)Math.ceil(dist);
        System.out.println(ans);
        }
    }
}