import java.io.*;

import java.util.StringTokenizer;


public class Q3 {
    
    public static void main(String[] args)throws IOException{
         BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
         PrintWriter writer=new PrintWriter(System.out);
         StringTokenizer st=new StringTokenizer(br.readLine()," ");
         int r=Integer.parseInt(st.nextToken());
         int x1=Integer.parseInt(st.nextToken());
         int y1=Integer.parseInt(st.nextToken());
         int x2=Integer.parseInt(st.nextToken());
         int y2=Integer.parseInt(st.nextToken());
         double d=Math.sqrt((long)(x1-x2)*(x1-x2)+(long)(y1-y2)*(y1-y2));
         double dd=d/(2*r);
         long ans= (long) Math.ceil(dd);
         writer.println(ans);
         writer.flush();
    }
}
