

import java.io.*;

/**
 * Created by DELL on 15-Nov-15.
 */
public class AmrAndPins
{
    public static void main(String arg[])
    {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;

        BufferedReader in = new BufferedReader(new InputStreamReader(inputStream));
        PrintWriter out = new PrintWriter(outputStream);

        try
        {
            String tokens[] = in.readLine().split(" ");
            int diameter = 2 * Integer.parseInt(tokens[0]);
            int x1 = Integer.parseInt(tokens[1]);
            int y1 = Integer.parseInt(tokens[2]);
            int x2 = Integer.parseInt(tokens[3]);
            int y2 = Integer.parseInt(tokens[4]);
            out.println((int) Math.ceil(Math.sqrt(Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2)) / diameter));
        } catch (IOException e)
        {
            e.printStackTrace();
        }
        out.close();
    }
}
