import java.io.*;
import java.util.*;

import static java.lang.Math.min;
import static java.lang.Math.max;
import static java.lang.Math.abs;

public class Main {

	static Scanner scn = new Scanner(System.in);
	static StringBuilder sb = new StringBuilder();
	static PrintWriter out = new PrintWriter(System.out);

	// https://codeforces.com/problemset?order=BY_RATING_ASC&tags=1400-1400

	public static void main(String[] HastaLaVistaLa) {
		int t = 1;
		for(int tests = 0; tests < t; tests++) solve();
		out.println(sb);
		out.close();
	}

	public static void solve() {
		// Road To Specialist Day 35
		double r = scn.nextDouble(), x = scn.nextDouble(), y = scn.nextDouble(), 
		x1 = scn.nextDouble(), y1 = scn.nextDouble();
		double dist = dist(x, y, x1, y1);
		if(x1 == x && y1 == y) sb.append(0);
		else if(dist < 2 * r) sb.append(2);
		else {
			r = 2 * r;
			dist = (double) Math.ceil(dist);
			long ans = (long) (dist / r);
			if(dist % r != 0) ans++;
			sb.append(ans);
		}

	}
	public static double dist(double x1, double y1, double x2, double y2) {
		double a = (x1 - x2), b = (y2 - y1);
		double dist = (a * a + b * b);
		return (double) Math.sqrt(dist);
	}
}