#include <algorithm>
#include <iostream>

using namespace std;

const int N = 1e5 + 5;
int n, a, b[N], k[N];

int pre(int x) {
  return (x + n - 1) % n;  
}

int next(int x) {
  return (x + 1) % n;
}

void solve() {
  cin >> n >> a;
  int ans = 3 * n;
  for (int i = 0; i < n; i++) cin >> b[i];
  for (int i = 0; i < n; i++) {
    int prev = pre(i);
    int nxt = next(i);
    int ones = b[prev] + b[i] + b[nxt];
    // int t = 2 * (b[prev] + b[i] + b[nxt]) - 3;
    k[i] =  -(3 - ones);
  }

  partial_sort(k, k + a, k + n, greater<int>());
  // sort(k, k + n, greater<int>());
  for (int i = 0; i < a; i++) ans += k[i];
  printf("%d\n", ans);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);

  solve();
  
}