#include <iostream>
#include <vector>
using namespace std;

int main()
{
    long long n, k, db=0;
    cin >> n >> k;

    long long ret;
    vector <int> retek;
    
    for (int i = 0; i < n; i++)
    {
        cin >> ret;
        if (ret == 1)
        {
            db++;
        }

    }

    long long resz = 0;

    while (k <= db)
    {
        resz += db-k+1;
        k ++;
    }

    cout << resz;

    return 0;
}