#include using namespace std; #include using namespace atcoder; using ll = long long; using VI = vector; using VVI = vector; using VL = vector; using VVL = vector; using VS = vector; using VVS = vector; using P = pair; using VP = vector

; #define rep(i, n) for (ll i = 0; i < ll(n); i++) #define out(x) cout << x << endl #define dout(x) cout << fixed << setprecision(10) << x << endl; #define all(a) (a).begin(),(a).end() #define rall(a) (a).rbegin(),(a).rend() #define sz(x) (int)(x.size()) #define re0 return 0 #define pcnt __builtin_popcount template inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; } template inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; } //const int INF = 1001001001; const ll INF = 1e18; //using mint = modint1000000007; //using mint = modint998244353; int di[8] = {0,0,-1,1,1,1,-1,-1}; int dj[8] = {1,-1,0,0,1,-1,1,-1}; #pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") int main(){ ios::sync_with_stdio(false); std::cin.tie(nullptr); ll n,k; cin >> n >> k; VL a(n); rep(i,n) cin >> a[i]; ll ans = 0; ll sum = 0; multiset st; for(int i = n-1;i > n-k;i--){ sum += a[i]; st.insert(a[i]); } for(int i = n-k;i >= 0;i--){ if(i%2 == 1){ chmax(ans,a[i]+sum); } if(*st.begin() < a[i]){ ll mn = *st.begin(); sum -= mn; sum += a[i]; st.erase(st.find(mn)); st.insert(a[i]); } } out(ans); }