import java.io.*;
import java.util.*;
import java.lang.*;
import java.math.*;
import java.text.*;

public class Main {  

    public static void main(String[] args) throws IOException  {
       
        //BufferedReader in = new BufferedReader(new FileReader(new File("D:/java.inp")));
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        
        String s[] = in.readLine().split(" ");
        int r = Integer.parseInt(s[0]);
        int x = Integer.parseInt(s[1]);
        int y = Integer.parseInt(s[2]);
        int i = Integer.parseInt(s[3]);
        int j = Integer.parseInt(s[4]);
        
        double d = Math.sqrt((x-i)*(x-i)+(y-j)*(y-j));
        int res = (int) Math.ceil(d/(2*r));
        
        System.out.print(res);
        
    }
    
} 
