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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;
//解説AC
int main() {
  string s;
  cin>>s;
  if(s.size()==1){
    cout<<s<<endl;
    return 0;
  }
  int kotae=s[0]-'0';
  bool hantei=false;
  for(int i=1;i<s.size();i++){
    if(s[i]=='9')hantei=true;
    else {
      hantei=false;
      break;
    }
  }
  kotae+=9*(s.size()-1);
  if(hantei==false)kotae--;
  cout<<kotae<<endl;
  return 0;
}