import java.util.Scanner;
public class test
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        double r=sc.nextDouble();
        double ans;
        double x=sc.nextDouble();
        double y=sc.nextDouble();
        double p=sc.nextDouble();
        double q=sc.nextDouble();
        double d=Math.sqrt((x-p)*(x-p)+(y-q)*(y-q));
        //System.out.println(d);
        if((d%(2*r))!=0.0)
        {
            ans=((d/r)/2)+1;
        }
        else
        {
            ans=(d/r)/2;
        }
        System.out.println((int)ans);
    }
}