/*   Created by IntelliJ IDEA.
 *   Author: Harsh Gautam (harsh822)
 *   Date: 22-04-2021
 *   Time: 22:20
 *   File: FoxAndSnake.java
 */

import java.util.*;

public class FoxAndSnake {
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        long r = scan.nextInt(), x = scan.nextInt(), y = scan.nextInt(), x1 = scan.nextInt(), y1 = scan.nextInt();
        System.out.println((int)(Math.ceil(Math.sqrt((x1-x)*(x1-x)+(y1-y)*(y1-y))/(2*r))));
    }
}
