import java.util.*;
import java.math.*;
import java.io.*;
public class A1
{
    public static void main(String args[]) throws IOException
    {
        Scanner sc=new Scanner(System.in);
        //int t=sc.nextInt();
        //while(t--!=0)
        {
            int r=sc.nextInt();
        int x=sc.nextInt();
        int y=sc.nextInt();
        int X=sc.nextInt();
        int Y=sc.nextInt();
        // z=Math.sqrt(Math.pow((x-X),2)+Math.pow((y-Y),2));
        int dist=(int)Math.ceil(Math.sqrt(Math.pow((x-X),2)+Math.pow((y-Y),2)));
        if(dist%(2*r)==0)
            System.out.println(dist/(2*r));
        else if(dist<(2*r))
            System.out.println("1");
        else if(dist%(2*r)!=0)
            System.out.println(dist/(2*r)+1);
        }
        
    }
}
