#include <iostream>
#define int long long
#define MOD 1000000001
using namespace std;

signed main(){
	int n,cnt,res = 0,last = 1;
	cin >> n;
	if(n <= MOD){
		cout << 0 << endl;
		return 0;
	} 
	cnt = n / MOD;
	while(last <= cnt) last = last * 10 + 1;
	last /= 10;
	cnt = (int)(cnt / last) * last;
	last = cnt;
	res += cnt % 10;
	cnt /= 10;
	while(cnt){
		cnt /= 10;
		res += 9;
	}
	if(MOD * last > n) res--;
	cout << res << endl;
	return 0;
}