B'You are given a positive integer n . Let S(x) be sum of digits in base 10 representation of x , for example, S(123) = 1 + 2 + 3 = 6 , S(0) = 0 . Your task is to find two integers a, b , such that 0 <= q a, b <= q n , a + b = n and S(a) + S(b) is the largest possible among all such pairs. The only line of input contains an integer n (1 <= q n <= q 10^{12}) . Print largest S(a) + S(b) among all pairs of integers a, b , such that 0 <= q a, b <= q n and a + b = n . 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. '...