//package com.company;
import java.io.*;
import java.util.*;

public class Main {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        PrintWriter pw = new PrintWriter(System.out);
        StringTokenizer st = new StringTokenizer(br.readLine());
        int r=Integer.parseInt(st.nextToken()),x1=Integer.parseInt(st.nextToken()),y1=Integer.parseInt(st.nextToken()),x2=Integer.parseInt(st.nextToken()),y2=Integer.parseInt(st.nextToken());
        double d = Math.sqrt(Math.pow(x1-x2,2)+Math.pow(y1-y2,2));
        pw.println((int)Math.ceil(d/(2*r)));
        pw.flush();
        pw.close();
    }
}