#include <bits/stdc++.h>

#include <variant>

#define rep2(i, k, n) for (i64 i = (i64)(k); i < (i64)(n); i++)
#define rep(i, n) rep2(i, 0, n)
#define all(x) begin(x), end(x)
#ifdef ENV_LOCAL
#define dump \
  if (1) cerr
#else
#define dump \
  if (0) cerr
#endif

using namespace std;
using namespace std::string_literals;

using i32 = int32_t;
using i64 = int64_t;
using f64 = double;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;

// using namespace harudake;

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  i64 n, k;
  cin >> n >> k;
  vi64 a(n);
  rep(i, n) cin >> a[i];
  priority_queue<i64, vector<i64>, greater<i64>> q;
  i64 sum = 0;
  i64 ans = 0;
  rep(ri, n) {
    i64 i = n - 1 - ri;
    q.push(a[i]);
    sum += a[i];
    if (size(q) > k) {
      sum -= q.top();
      q.pop();
    }
    dump << sum << endl;
    if (size(q) == k && (i + 1) % 2 == 0) {
      if (q.top() > a[i]) {
        ans = max(ans, sum - q.top() + a[i]);
      } else {
        ans = max(ans, sum);
      }
    }
  }
  cout << ans << endl;
  return 0;
}