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 <iostream>
#include <vector>

using namespace std;

typedef long long ll;

int main()
{
    ll n;
    int ans;
    bool nine;
    vector<int> n_;
    cin >> n;

    nine = true;
    int i = 0;
    while (n >= 1)
    {
        n_.push_back(n % 10);
        if (n >= 10 && n_.back() != 9)
            nine = false;
        n /= 10;
        i++;
    }

    if (nine)
        ans = n_.back() + (n_.size() - 1) * 9;
    else
        ans = (n_.back() - 1) + (n_.size() - 1) * 9;

    cout << ans << endl;

    return 0;
}