import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author testing
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        BAmrAndPins solver = new BAmrAndPins();
        solver.solve(1, in, out);
        out.close();
    }

    static class BAmrAndPins {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            String input = in.nextLine();
            String[] token = input.split(" ");
            double epsilon = 10e-3;
            int r = Integer.parseInt(token[0]);
            int x = Integer.parseInt(token[1]);
            int y = Integer.parseInt(token[2]);
            int x1 = Integer.parseInt(token[3]);
            int y1 = Integer.parseInt(token[4]);
            int d = r * 2;
            int minStep = 0;

            double dist = dist(x, y, x1, y1);

            if (dist < epsilon) {
                ;
            } else {
                // done
                ;

                dist -= r;
                if (dist % d > r)
                    minStep++;

                if (dist % d >= epsilon)
                    minStep++;
                minStep += (int) dist / d;
            }

            out.println(minStep);


        }

        public double dist(int x, int y, int x1, int y1) {
            return Math.sqrt(Math.pow(x1 - x, 2) + Math.pow(y1 - y, 2));
        }

    }
}

