#include <iostream>
using namespace std;
int main()
{
	int a = 0,b = 0;
	for (int i = 1; i <= 12; i++)
	{
		for (int j = 1; j <= 30; j++)
		{
			a = j / 10 + j % 10;
			if (i == a) b++;
		}
	}
	cout<< b << endl;
	return 0;
}