public static int countDigit(int n, int d) {
        int cnt = 0;
        long i = 1; //位数
        while (n / i > 0) {
            long leading = n / (i * 10);
            long rest = n % i;
            long curr = n % (i * 10) / i;

            if (d != 0)
                cnt += leading  * i;
            else {
                cnt += leading == 0 ? 1 : (leading - 1) * i; 
            }

            // avoid leading 0s
            if ((d != 0 || leading > 0) && (d != 0 || i != 1)) {
                if (curr > d)
                    cnt += i;
                else if (curr == d)
                    cnt += rest + 1;
            }
            i *= 10;
        }
        return cnt;
    }