/*
If you want to aim high, aim high
Don't let that studying and grades consume you
Just live life young
*/
import java.util.*;
import java.io.*;

   public class Ladder11
   {
      public static void main(String args[]) throws Exception
      {
         BufferedReader infile = new BufferedReader(new InputStreamReader(System.in));  
         StringTokenizer st = new StringTokenizer(infile.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 dist = ((long)X2-X1)*(X2-X1)+((long)Y2-Y1)*(Y2-Y1);
         dist = Math.sqrt(dist);
         double res = dist/(2*R);
         if((long)res != res)
            res++;
         System.out.println((long)res);
      }
      public static void sort(int[] arr)
      {
         //stable heap sort
         PriorityQueue<Integer> pq = new PriorityQueue<Integer>();
         for(int a: arr)
            pq.add(a);
         for(int i=0; i < arr.length; i++)
            arr[i] = pq.poll();
      }
   }