// package CodeForces;

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

public class Problem_507B {
	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner();
		PrintWriter pw = new PrintWriter(System.out);
		int r=sc.nextInt(),x1=sc.nextInt(),y1=sc.nextInt(),x2=sc.nextInt(),y2=sc.nextInt();
		double d=Math.sqrt(Math.abs(y2-y1)*Math.abs(y2-y1)+Math.abs(x2-x1)*Math.abs(x2-x1));
		int ans=0;
		while(d>0)
		{
			d-=2*r;
			ans++;
		}
		System.out.println(ans);
		pw.close();
	}

	static class Scanner {
		BufferedReader br;
		StringTokenizer st;

		Scanner() {
			br = new BufferedReader(new InputStreamReader(System.in));
		}

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

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

		long nextLong() throws IOException {
			return Long.parseLong(next());
		}

		double nextDouble() throws IOException {
			return Double.parseDouble(next());
		}

		String nextLine() throws IOException {
			return br.readLine();
		}

		boolean hasnext() throws IOException {
			return br.ready();
		}

	}
}
