#include<bits/stdc++.h>
#define int long long

using namespace std;

signed main() {
	int n, k;

	cin >> n >> k;

	vector<int> a(n);

	for (int &u: a) {
		cin >> u;
	}

	vector<int> cnt(n);

	for (int i = 0 ; i < n ; i++) {
		if (a[i] == 0) {
			cnt[(i-1+n)%n]++;
			cnt[(i+1+n)%n]++;
			cnt[i]++;
		}
	}

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

	int res = 3 * n;

	for (int i = 0 ; i < k ; i++) {
		res -= cnt[i];
	}

	cout << res;
}