import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;

public class AmrAndPins {

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        OutputStream out = new BufferedOutputStream(System.out);

        String[] l = br.readLine().split("\\s+");
        int r = Integer.parseInt(l[0]);
        int x = Integer.parseInt(l[1]);
        int y = Integer.parseInt(l[2]);
        int x_ = Integer.parseInt(l[3]);
        int y_ = Integer.parseInt(l[4]);

        double d = Math.sqrt(((x - x_) * (x - x_)) + ((y - y_) * (y - y_)));

        int res = (int) Math.ceil(d / (2 * r));

        out.write((res + "\n").getBytes());

        out.flush();
        br.close();

    }

}
