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



public class Test {
    
    public static void main(String[] args) throws Exception {
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String s[] = in.readLine().split(" ");
        Long r = Long.parseLong(s[0]);
        Long x = Long.parseLong(s[1]);
        Long y = Long.parseLong(s[2]);

        long xd = Long.parseLong(s[3]);
        long yd = Long.parseLong(s[4]);
        Long xs = (Long)((xd-x)*(xd-x));
        Long ys = (Long)((yd-y)*(yd-y));
        long ans = (long)Math.ceil((Math.sqrt(xs*1.0+ys*1.0)*1.0)/(2.0*r));
        System.out.println(ans);



    } 
}