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<stdio.h>
#include<iostream>
#include<stdlib.h>
#include<string.h>
using namespace std;
#define ll long long
int main(void)
{
	ll n,nn,j,k,e;
	cin>>n;
	nn=n;j=0;k=0;e=1;while(nn>=10){k++;nn/=10;j=j*10+9;e*=10;}
	if(nn*e+j<=n)cout<<nn+k*9;
	else cout<<nn-1+k*9;
	return 0;
}