#include "iostream"
#include "cmath"
#include "algorithm"
#include "string"
#include "vector"
using namespace std;

int s = 0;

void output() {
	cout << s << endl;
}

int main() {
	int a, b;

	for (int i = 0; i < 13; i++) {
		for (int j = 0; j < 30; j++) {

			a = j / 10;
			b = j - (10 * a);

			if (i == a + b) {
				s += 1;
			}
		}
	}


	output();

	return 0;
}