
//package codeForcesPractice;

import java.util.Scanner;

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