Maximum Sum of Digits

Description:

Input:

The only line of input contains an integer $$$n$$$ $$$(1 \leq n \leq 10^{12})$$$.

Output:

Print largest $$$S(a) + S(b)$$$ among all pairs of integers $$$a, b$$$, such that $$$0 \leq a, b \leq n$$$ and $$$a + b = n$$$.

Sample Input:

35

Sample Output:

17

Sample Input:

10000000000

Sample Output:

91

Note:

In the first example, you can choose, for example, $$$a = 17$$$ and $$$b = 18$$$, so that $$$S(17) + S(18) = 1 + 7 + 1 + 8 = 17$$$. It can be shown that it is impossible to get a larger answer.

In the second test example, you can choose, for example, $$$a = 5000000001$$$ and $$$b = 4999999999$$$, with $$$S(5000000001) + S(4999999999) = 91$$$. It can be shown that it is impossible to get a larger answer.