---

#include <iostream>

using namespace std;

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int l, n;
    cin >> l >> n;

    int count = 0;
    int skip = 0;

    for (int i = 0; i < n; ++i) {
        int board;
        cin >> board;

        if (skip > 0) {
            skip--;
        } else if (board == 1) {
            count++;
            skip = l - 1;
        }
    }

    cout << count << "\n";

    return 0;
}