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: Wrong Answer)

    #include<iostream>
    #include<stdio.h>
    //#include <bits/stdc++.h>
    #include<vector>
    #include<float.h>
    #include<iomanip>
    #include<algorithm>
    #include<string>
    #include<cstring>
    #include<math.h>
    #include<cmath>
    #include<sstream>
    #include<set>
    #include<map>
    #include<queue>
    #include<cassert>
    #include<cmath>
    #include<cstdint>
    #include<numeric>
    #include<array>
     
    #define INF 1e9
    #define rep(i,n)for(int i=0;(i)<(int)(n);i++)
    #define REP(i,a,b)for(int i=(int)(a);(i)<=(int)(b);i++)
    #define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
    #define vec(type,n) vector<type>(n)
    #define vvec(m,n) vector<vector<int>> (int(m),vector<int>(n))
    #define ALL(a)  (a).begin(),(a).end()
    #define chmin(a, b) a = min(a, b)
    #define chmax(a, b) a = max(a, b)
    #define Vl vector<ll>
     
    using namespace std;
    using ll = long long;
    using Graph = vector<vector<int>>;
    using P = pair<ll, ll>;
     
const ll MOD = 1e9 + 7;
const ll ZER = 0;

int main(){
   string s;
   cin >> s;
   ll n = s.size();
   
   ll res = 0, sum = 0;
   rep(i, n){
       sum += (s[i] - '0');
       if(s[i] != '0'){
           chmax(res, sum + (n - i - 1) * 9 - 1);
       }
   }
   cout << res << endl;
}