#include <iostream>
using namespace std;

int main(){
	long long n, ans = 0;
	cin >> n;
	for(long long i = 1; (1e9 + 1) * i <= n; i *= 10, i++){
		for(int j = 1; j <= 9; j++){
			if(n < (1e9 + 1) * i * j) continue;
			ans++;
		}
	}
	cout << ans << endl;
}