import java.io.*;
import java.util.*;
public class codeforces
{    
    public static void main(String args[])
    {
        //PrintWriter out=new PrintWriter(System.out);
        Scanner sc = new Scanner(System.in);
        int n=sc.nextInt();
        int x1=sc.nextInt();
        int y1=sc.nextInt();
        int x2=sc.nextInt();
        int y2=sc.nextInt();
        System.out.println((int)Math.ceil((Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1))/2.0/n)));
    }
}