#include <iostream>		//cin, cout
#include <vector>		//vector
#include <algorithm>	//sort,min,max,count
#include <string>		//string,getline, to_string
#include <cstdlib>		//abs(int)

using namespace std;

int main() {

	int ans = 0;
	int temp;

	for (int i = 1; i <= 12; i++) {
		for (int j = 1; j <= 31; j++) {
			temp = (j / 10) + (j % 10);
			if (i == temp) {
				ans++;
			}
		}
	}

	ans--; //4/31

	cout << ans << endl;

	return 0;

}