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: Wrong Answer)

#include<iostream>
int main(){
int n,sum=28,a=1000;
  std::cin>>n;
  for(int i=1000;i*10<=n;i*=1000){
    sum+=27;
    a=i;
  }
  for(int i=a;i>a;i/=10){
  sum-=9;
    a=i;
  }
  std::cout<<sum+n/a-1<<std::endl;
}