#include <iostream>
#include <vector>

using namespace std;

vector<int> vals;

int main()
{
	int n, k;
	cin >> n >> k;
	for (int i = 0; i < n; i++)
	{
		int x;
		cin >> x;
		if (x == 1)
		{
			vals.push_back(i + 1);
		}
	}

	int ans = 0;

	for (int i = 0; i < vals.size(); i++)
	{
		ans += max(0, int(vals.size() - i - k + 1));
	}
	cout << ans;
}