#include<bits/stdc++.h>
using namespace std;

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	string s;
	cin>>s;
	int sum=0;
	for(auto it:s)
		sum+=it-'0';
	int sum2=s[0]-'1'+(s.size()-1)*9;
	cout<<max(sum,sum2)<<endl;
}
