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;
#define ll long long

int main(){
    string S;
    cin >> S;
    int d = S.size();
    if (d == 1) cout << S << endl;
    else {
        if (count(S.begin()+1, S.end(), '9') == d-1) {
            cout << (int)(S[0]-'0') + 9*(d-1) << endl;
        } else cout << (int)(S[0]-'0'-1) + 9*(d-1) << endl;
    }
    return 0;
}