/**
 * @(#)lion.java
 *
 *
 * @author
 * @version 1.00 2015/11/19
 */

import java.io.*;
import java.util.*;
import java.math.*;
public class lion {

    public static void main(String []args) throws IOException{
    	BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st=new StringTokenizer(in.readLine());
    int r=Integer.parseInt(st.nextToken());
    int x1=Integer.parseInt(st.nextToken());
    int y1=Integer.parseInt(st.nextToken());
    int x2=Integer.parseInt(st.nextToken());
    int y2=Integer.parseInt(st.nextToken());
    double dist_x=Math.pow(Math.abs(x2-x1),2);
     double dist_y=Math.pow(Math.abs(y2-y1),2);
    double d=Math.sqrt(dist_y+dist_x);
   // System.out.println(d/(r*2));
    double x=Math.round(d/(r*2));
    if(x*r*2>=d)
    	System.out.println((int)x);
    else{	x++;
    	System.out.println((int)x);
    }}
    }

