import java.io.*;
public class Main {

    public static void main(String[] args) {
        try {
            //READING PART
            BufferedReader br = new BufferedReader(new FileReader("fractii.in"));
            int n = Integer.valueOf(br.readLine());
            br.close();
            int res = 1, i,j;

            for (i = 2; i <= n; i++) {
                double sqrt_f  = Math.sqrt(i);
                int sqrt = (int) Math.floor(sqrt_f);
                int count = i == sqrt * sqrt ? 2 : 1;
                for (j = 2; j < sqrt_f; j ++) {
                    count += i % j == 0 ? 2: 0;
                }
                res = res + 2 * ( i - count);
                //System.out.println(i +" -> " + "factors:  " + count + "res: "+ res );
            }

            BufferedWriter bw = new BufferedWriter(new FileWriter("fractii.out"));
            bw.write(String.valueOf(res));
            bw.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}