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>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<string>
#include<sstream>
#include<cmath>
#include<numeric>
#include<map>
#include<stack>
#include<queue>
#include<list>
#include<set>
#include<cstring>
using namespace std;
long long int mod = 1e9 + 7;
template <class T>
void inputV(vector<T> &x, int n){
  for(int i=0; i<n; i++) cin >> x[i];
}

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

  return 0;
}



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