import java.io.*;
import java.util.*;
public class AmrAndPins {
static StringTokenizer st;
 static BufferedReader in;
 static PrintWriter out;


 private static int nextInt() throws IOException 
 {
        return Integer.parseInt(next());
 }

  private static long nextLong() throws IOException
  {
        return Long.parseLong(next());
  }
  private static byte nextByte() throws IOException
  {
        return Byte.parseByte(next());
  }
  
   private static String next() throws IOException
 {
        while(st == null || ! st.hasMoreTokens())
        {
            st = new StringTokenizer(in.readLine());
        }
        return st.nextToken();
 }
   
 
  
    public static void  main(String[] args) throws IOException 
    {
        in = new BufferedReader(new InputStreamReader(System.in));
        out = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
            int r=nextInt();
            int x1=nextInt();
            int y1=nextInt();
            int x2=nextInt();
            int y2=nextInt();
            double distance = Math.sqrt(Math.pow(Math.abs(x2 - x1), 2) + Math.pow(Math.abs(y2 - y1), 2));
            int ans=(int)Math.ceil(distance / (2 * r));
            
            
            System.out.println(ans);
    }
    
}
