Problem:
Score : 300 points

Problem Statement

Find the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Constraints

1\leq N \leq 10^{16}

N is an integer.

Input

Input is given from Standard Input in the following format:

N

Output

Print the maximum possible sum of the digits (in base 10) of a positive integer not greater than N.

Sample Input 1

100

Sample Output 1

18

For example, the sum of the digits in 99 is 18, which turns out to be the maximum value.

Sample Input 2

9995

Sample Output 2

35

For example, the sum of the digits in 9989 is 35, which turns out to be the maximum value.

Sample Input 3

3141592653589793

Sample Output 3

137

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <cstdio>
#include <cstdint>
#include <vector>
#include <string>

int main() {
  char buf[32];
  scanf("%s", buf);
  std::string s = buf;

  int res = 0;
  for (size_t i = 0; i < s.length(); ++i)
    res += s[i]-'0';

  --s[0];
  for (size_t i = 1; i < s.length(); ++i) s[i] = '9';
  int cur = 0;
  for (size_t i = 0; i < s.length(); ++i)
    cur += s[i]-'0';

  res = std::max(res, cur);
  printf("%d\n", res);
}