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# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Linq;

class Program
{
    static void Main(string[] args) {
        long n = long.Parse(Console.ReadLine());
        long l = digitLength(n);
        long s = -1;
        for(long i = 1; i <= l; i++) {
            long d = 1;
            for(long j = 1; j <= i; j ++) d += 10L*j;
        }
        long[] sums = new long[n-s+1];
        for(long i = s; i <= n; i ++) {
            sums[i-s] = digitSum(i);
        }
        Console.WriteLine(sums.Max());
    }
    static long digitLength(long x) {
        long length = 0;
        while(x>0) {
            length++;
            x /= 10;
        }
        return length;
    }
    static long digitSum(long x) {
        long sum = 0;
        while(x>0) {
            sum += x%10;
            x/=10;
        }
        return sum;
    }
}