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

using i64 = long long;

int main() {
    cin.tie(nullptr)->sync_with_stdio(false);

#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    auto solve = [&]() {
        int n, k;
        cin >> n >> k;

        vector<int> b(n);
        for (int i = 0; i < n; i++) {
            cin >> b[i];
        }

        int ans = 3 * n;

        vector<int> d(n);
        for (int i = 0; i < n; i++) {
            for (int j : {i, (i + 1) % n, (i + n - 1) % n}) {
                d[i] += b[j] == 0;
            }
        }

        sort(d.begin(), d.end());

        cout << 3 * n - accumulate(d.begin(), d.begin() + k, 0) << '\n';
    };
    
    solve();
    
    return 0;
}