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

int n, k, i, db;
vector<int> x, y;

int main()
{
    cin >> n >> k;

    x.resize(n + 1);

    for (i = 1; i <= n; ++i)
    {
        cin >> x[i];
        if (x[i] == 1)
        {
            ++db;
            y.push_back(i);
        }
    }

    if (db < k)
    {
        cout << 0;
        return 0;
    }
    else if (db == k)
    {
        cout << 1;
        return 0;
    }

    db = 0;
    for (i = 0; i < y.size() - 2; ++i)
    {
        db += y.size() - (i + 2);
    }

    cout << db;
}