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;
typedef long long ll;
#define rep(i,n) for(ll (i)=0;(i)<(n);(i)++)

int main(){
    ll N;
    cin>>N;
    string s = to_string(N);
    ll d = s.length();
    for(ll i=1; i<d; i++){
        s[i] = '9';
    }
    if(stoll(s) > N) s[0] = s[0] - 1;
    ll sum=0;

    rep(i, d) sum+=s[i] - '0';
    cout << sum << endl;
    return 0;
}