#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <cmath>
#include <stack>
#include <set>
#include <map>
typedef long long ll;
typedef unsigned int uint;
using namespace std;


int main() {
	int count = 0;
	for (int i = 0; i <= 12; i++) {
		for (int j = 0; j <= 31; j++) {
			if (i == (j / 10) + (j % 10))
				count++;
		}
	}
	// 4/31
	cout << count - 1 << endl;
}