#include <iostream>

using namespace std;
int d, r;
int genPas(int r)
{
    int p = 1, count = 0;
    int c = r;
    for(int i = 1; i <= r; i++)
    {

        p *= c;
        p /= i;
        c--;
        if(p%d == 0)
        {
            count++;
        }
    }
    return count;
}

int main()
{
    //cin >> r >> d;
    r = 20;
    d = 3;
    cout << genPas(r);
    return 0;
}