import java.util.Scanner;
public class amr
{
    public static void main(String args[])
    {
        Scanner sc=new Scanner(System.in);
        int r=sc.nextInt();
        int x1=sc.nextInt();
        int y1=sc.nextInt();
        int x2=sc.nextInt();
        int y2=sc.nextInt();
        int dia=2*r;
        double z=Math.pow((x1-x2),2)+Math.pow((y1-y2),2);
        double dist=Math.sqrt(z);
        int q=(int)(dist/dia);
        double remainder=dist%dia;
        if (remainder==0)
        {
            System.out.println(q);
        }
        else
        {
            System.out.println(q+1);
        }
    }
}
