#include <bits/stdc++.h>
using namespace std;

int main() {
    int N;
	int K;
    cin >> N >> K;

    vector<int> dijas_varosok;
    for (int i = 0; i < N; i++) {
        int toll;
        cin >> toll;
        if (toll == 1) {
            dijas_varosok.push_back(i);
        }
    }

    int total_routes = 0;

    for (int i = 0; i < dijas_varosok.size(); i++) {
        for (int j = i + 1; j < dijas_varosok.size() && (j - i + 1) <= K; ++j) {
            total_routes++;
        }
    }

    cout << total_routes << endl;
}