#include <bits/stdc++.h>
#define int long long
using namespace std;
int n;
int check(int x){
	int num=-1;
	int t=0;
	while (x){
		t=x%10;
		x/=10;
		num++;
	}
	return num*9+t;
}
signed main ()
{
	freopen("palindrome.in","r",stdin); 
	freopen("palindrome.out","w",stdout); 
	cin>>n;
	int x=n/1000000001;
	cout<<check(x);
	return 0;
}