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(" ");
        int r = Integer.parseInt(s[0]);
        int x = Integer.parseInt(s[1]);
        int y = Integer.parseInt(s[2]);

        int xd = Integer.parseInt(s[3]);
        int yd = Integer.parseInt(s[4]);
        int xs = (xd-x)*(xd-x);
        int ys = (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);



    } 
}