#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll mod = 1e9 + 7;
const ll inf = (1 << 30) - 1;
const ll infll = (1LL << 61) - 1;

int a, b;

int main()
{
    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;
}