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>

using namespace std;


int main(void){
	unsigned long n,a=0,s=0;

	cin >> n;

	if(n < 10)a = n;
	else {
		while(n>=10){
			s=s+n%10;
			n=n/10;
			a=a+9;
		}
	a = a + n - 1;
	s = s+n%10;
	a = max(a,s);
	}

	cout << a << endl;

	return 0;
}