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

public class Main {

    final int mod = 1000000007;

    public static void main(String args[]) throws FileNotFoundException {
        try {
            File in = new File("input.txt");
            Scanner sc;
            if (in.exists()) {
                PrintStream out = new PrintStream(new File("output.txt"));
                sc = new Scanner(new File("input.txt"));
                System.setOut(out);
            } else {
                sc = new Scanner(System.in);
            }

            int t = 1;
            // t = sc.nextInt();
            while (t-- > 0) {
                double r, x1, y1, x2, y2;
                r = sc.nextDouble();
                x1 = sc.nextDouble();
                y1 = sc.nextDouble();
                x2 = sc.nextDouble();
                y2 = sc.nextDouble();

                double dist = Math.sqrt(Math.pow((x1 - x2), 2) + Math.pow((y1 - y2), 2));
                System.out.println((int) Math.ceil(dist / (2 * r)));
            }
        } catch (Exception e) {
            return;
        }
    }
}