import java.io.IOException;
import java.util.Arrays;
import java.util.Scanner;


public class cod {
     public static void main(String args[]) throws IOException{
     Scanner s=new Scanner(System.in);
     int r=s.nextInt();
     int x=s.nextInt();
     int y=s.nextInt();
     int m=s.nextInt();
     int n=s.nextInt();
     double w=(x-m)*(x-m);
     double q=(y-n)*(y-n);
     double sq=Math.sqrt(w+q);
     double to=sq/(2*r);
     to=Math.ceil(to);
     int re=(int)to;
     System.out.println(re);
     }
}
