/*
    Aman Agarwal
    algo.java
*/

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

public class B507
{
    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;
            }
    }


    static FastReader sc = new FastReader();
    static PrintWriter out = new PrintWriter(System.out);
    
    public static void main(String[] args) 
    {
        int t = 1;
        //t = sc.nextInt();
        while(t-- > 0)
        {
            int r = sc.nextInt();
            int x1 = sc.nextInt();
            int y1 = sc.nextInt();
            int x2 = sc.nextInt();
            int y2 = sc.nextInt();

            
            double d = Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
            
            out.println((int)(Math.ceil(d/(2*r))));
            out.flush();

        }    
    }
}
