#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
using ll = long long;
using namespace std;
const int INF = 1e9;

int main() {

    int ans = 0;
    for (int i = 1; i <= 31; ++i) {
        if (i % 10 + i / 10 <= 12)
            ++ans;
    }

    cout << ans - 1 << endl;

    return 0;
}