public class Euler159 {
    static int digitalRoot(int n) {
        return n == 0 ? 0 : 1 + (n - 1) % 9;
    }

    public static void main(String[] args) {
        int limit = 1000000;
        int[] mdrs = new int[limit];
        for (int n = 1; n < limit; n++)
            mdrs[n] = digitalRoot(n);
        for (int a = 2; a < limit; a++)
            for (int p = a * 2; p < limit; p += a) {
                int cand = mdrs[a] + mdrs[p / a];
                if (cand > mdrs[p])
                    mdrs[p] = cand;
            }
        long sum = 0;
        for (int n = 2; n < limit; n++)
            sum += mdrs[n];
        System.out.println(sum);
    }
}