import java.io.PrintWriter;
import java.util.Scanner;

public class Main {

	public static Scanner sc;
	public static PrintWriter pw;
	
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		pw = new PrintWriter(System.out);
		
		new Main().run();
		
		sc.close();
		pw.flush();
		pw.close();
	}
	
	private void run() {
		readData();
		solve();
	}
	
	private double EPS = 0.0000000001;
	private int r, x1, y1, x2, y2;
	
	private void readData() {
		r = sc.nextInt();
		x1 = sc.nextInt();
		y1 = sc.nextInt();
		x2 = sc.nextInt();
		y2 = sc.nextInt();
	}
	
	private void solve() {
		double dist = Math.sqrt((x1-x2) * (x1-x2) + (y1-y2) * (y1-y2));
		r *= 2;
		
		if (dist % r < EPS ) {
			pw.println((int)(dist / r));
		} else {
			pw.println((int)(dist / r) + 1);
		}
	}
}
