

import java.io.*;
import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class Main1 {

    static final long mod =  1000000007 ;



    public static void main(String[] args) {

        try {


            FastScanner in = new FastScanner();
            PrintWriter out = new PrintWriter(System.out);


             int r = in.nextInt() ;
             int x = in.nextInt() ;
             int y = in.nextInt() ;
             int x1 = in.nextInt() ;
             int y1 = in.nextInt() ;

            double d = Math.sqrt(  (x-x1)*(x-x1) + (y-y1)*(y-y1)) ;

            System.out.println((int)Math.ceil(d/(double) (2*r)));

















            out.flush();
            out.close();


        } catch (Exception e) {
            return;
        }


    }



    static int gcd(int a, int b) {
        if (b > a) {
            int tenp = b;
            b = a;
            a = tenp;
        }
        int temp = 0;
        while (b != 0) {
            a %= b;
            temp = b;
            b = a;
            a = temp;
        }
        return a;
    }

    static long gcd_long(long a, long b) {
        if (b > a) {
            long tenp = b;
            b = a;
            a = tenp;
        }
        long temp = 0;
        while (b != 0) {
            a %= b;
            temp = b;
            b = a;
            a = temp;
        }
        return a;
    }














    static class FastScanner {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer("");

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

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

        int[] readArray(int n) {
            int[] a = new int[n];
            for (int i = 0; i < n; i++) a[i] = nextInt();
            return a;
        }


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


}







