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 <bits/stdc++.h>
using namespace std;

int main(void){
    string s;
    cin>>s;
    
    int N=s.size();
    int top=s[0]-'0';
    
    int ans=(top-1)+9*(N-1);
    
    for(int i=1;i<N;i++){
        if(s[i]!='9')break;
        if(i==N-1){
            ans=top+9*i;
        }
    }
    
    if(N==1)ans=top;
    
    cout<<ans<<endl;
}