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 MAX(int a,int b){return a<b?b:a;}
int main(){
  char s[20];
  int max=0,l,i,a=0;
  scanf("%s",s);
  for(l=0;s[l];l++);
  for(i=0;i<l;i++){
    max=MAX(max,a+(s[i]-'0'-1)+(l-i-1)*9);
    a+=s[i]-'0';
  }
  printf("%d\n",MAX(max,a));
  return 0;
}