//package com.infmme.cf507;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

/**
 * infm created it with love on 1/25/15. Enjoy ;)
 */
public class SolutionB {
	private static double EPS = 0.0000005;

	public static void main(String[] args) {
		FastScanner in = new FastScanner();
		SolutionB.solve(in.nextInt(), in.nextInt(), in.nextInt(), in.nextInt(), in.nextInt());
	}

	public static class FastScanner {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st;

		String next() {
			while (st == null || !st.hasMoreTokens()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			return st.nextToken();
		}

		int nextInt() {
			return Integer.parseInt(next());
		}


		int read() throws IOException {
			return br.read();
		}
	}

	public static void solve(int r, int x, int y, int x1, int y1){
		double dist = Math.sqrt((x - x1) * (x - x1) + (y - y1) * (y - y1));
		double d = r * 2;
		if (dist < EPS)
			System.out.println(0);
		else if (dist - d < -EPS)
			System.out.println(2);
		else
			System.out.println((int)Math.ceil(dist / d));
	}
}
