#include <bits/stdc++.h> using namespace std; #include <atcoder/all> using namespace atcoder; using ll = long long; using vi = vector<int>; using vvi = vector<vector<int>>; using pii = pair<int, int>; #define rep(i, n) for (int i = 0; i < (int)(n); ++i) #define repr(i, n) for (int i = (int)(n - 1); i >= 0; --i) int main() { int n, K; cin >> n >> K; vi a(n); rep(i, n) cin >> a[i]; ll ret = 0; ll s = 0; priority_queue<ll, vector<ll>, greater<ll>> pq; repr(i, n) { if (pq.size() > K - 1) { s -= pq.top(); pq.pop(); } s += a[i]; pq.emplace(a[i]); if (i & 1) ret = max(ret, s); } cout << ret << endl; return 0; }