#include <algorithm>
#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	uint64_t N;
	cin >> N;
	uint64_t b = (uint64_t)1e9 + 1;
	//	1~9 : 9
	//	11~99 : 18
	//	111~999 :
	//	...
	//	11111111~99999999
	int cnt = 0;
	N /= b;
	uint64_t minval = 10;
	while (N > 0) {
		minval = min(minval, N % 10);
		cnt += N >= 10 ? 9 : 0;
		N /= 10;
	}
	cnt += minval;
	cout << cnt << endl;
	return 0;
}