/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
//package Codeforces;

/**
 *
 * @author Administrator
 */
import java.util.Scanner;
public class c507B {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int r = in.nextInt();
        int x1 = in.nextInt();
        int y1 = in.nextInt();
        int x2 = in.nextInt();
        int y2 = in.nextInt();
        double d = Math.hypot(x1-x2, y1-y2);
        int t = (int)d/(2*r);
        if (d > t*2*r) t++;
        System.out.println(t);
    }
}
