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

    public class Main {
        public static void main(String args[])
        {
            FastReader sc = new FastReader();
            PrintWriter pw = new PrintWriter(System.out);
            long r = sc.nextInt();
            r *= 2;
            long x = sc.nextInt();
            long y = sc.nextInt();
            long x1 = sc.nextInt();
            long y1 = sc.nextInt();
            double dis = Math.sqrt((x-x1)*(x-x1) + (y-y1)*(y-y1));
            pw.print((int)Math.ceil(dis / (double) r));
            pw.close();
        }


























        static class FastReader
        {
            BufferedReader br;
            StringTokenizer st;

            public FastReader()
            {
                br = new BufferedReader(new
                        InputStreamReader(System.in));
            }

            String next()
            {
                while (st == null || !st.hasMoreElements())
                {
                    try
                    {
                        st = new StringTokenizer(br.readLine());
                    }
                    catch (IOException  e)
                    {
                        e.printStackTrace();
                    }
                }
                return st.nextToken();
            }

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

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

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

            String nextLine()
            {
                String str = "";
                try
                {
                    str = br.readLine();
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
                return str;
            }
        }
    }