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: Wrong Answer)

#include<bits/stdc++.h>
using namespace std;
const long long INF = (1LL << 32);
const long long MOD = 1000000007;
const long double PI = 3.1415926;
#define FOR(i,r,n) for(ll i = (ll)(r); i < (ll)(n); i++)
#define RFOR(i,r,n) for(ll i=(ll)(n-1);i>=r;i--)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(x) x.begin(),x.end()
#define RALL(x) x.rbegin(),x.rend()
typedef long long int ll;
typedef vector<ll> vi;
typedef vector<pair<ll, ll>> vp;
typedef vector<string> vs;
typedef vector<char> vc;
typedef list<ll> lst;
typedef pair<ll, ll> P;
template <class T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <class T> T &chmax(T &a, const T &b) { return a = max(a, b); }

ll n, m, k, ans = 0, sum = 0, cnt = 0;
string s;
char c;

#define Endl endl

/*--------------------template--------------------*/


int main() {
    cin >> n;
    s = to_string(n);
    if(s[0]==1){
        cout << 9 * (s.size() - 1) << endl;
    }else{
        ll t = s[0] - '0' - 1;
        c = t + '0';
        string r;
        r += c;
        REP(i,s.size()-1) {
            r += '9';
        }
        if(s>r){
            cout << (s[0] - '0' - 1) + 9 * (s.size() - 1) << endl;
        }else{
            cout << (s[0] - '0') + 9 * (s.size() - 1) << endl;
        }
    }
}