import java.util.*;
import java.io.*;
import java.math.*;

public class BasicJava
{
   public BasicJava()
   {
   }
   
   public InputReader in = new InputReader(System.in);
   public PrintWriter out = new PrintWriter(System.out);
   
   public long sqr(long x)
   {
      return x * x;
   }
   
   public void run()
   {
      long r = in.nextLong();
      long x1 = in.nextLong();
      long y1 = in.nextLong();
      long x2 = in.nextLong();
      long y2 = in.nextLong();
      
      double d = Math.sqrt(sqr(x1 - x2) + sqr(y1 - y2));
      
      out.println((int)Math.ceil(d / (2 * r)));
      
      out.close();
   }
   
   public static void main(String[] args)
   {
      new BasicJava().run();
   }

   static class InputReader
   {
      public BufferedReader reader;
      public StringTokenizer tokenizer;

      public InputReader(InputStream stream)
      {
         reader = new BufferedReader(new InputStreamReader(stream), 32768);
         tokenizer = null;
      }

      public String next()
      {
         while (tokenizer == null || !tokenizer.hasMoreTokens())
         {
            try
            {
               tokenizer = new StringTokenizer(reader.readLine());
            }
            catch (IOException e)
            {
               throw new RuntimeException(e);
            }
         }
         return tokenizer.nextToken();
      }

      public int nextInt()
      {
         return Integer.parseInt(next());
      }

      public long nextLong()
      {
         return Long.parseLong(next());
      }

      public double nextDouble()
      {
         return Double.parseDouble(next());
      }

   }

}