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 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
int main(void){
    long int C,Q,R=0;
    long int j,h=0;
    scanf("%ld",&C);
    long int X[17];
    for(int i=0;i<17;i++){X[i]=0;}
    for(long int i=0;i<17;i++){
        X[i]=C%10;
        R+=X[i];
        C=(C-X[i])/10;
        if(C==0){j=i+1;break;}
    }
    Q=X[j-1]-1+9*(j-1);
    if(R==(Q+1)){
        printf("%ld\n",R);
    }else{
        printf("%ld\n",Q);
    }
    return 0;
}