#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
namespace my{
#define LL(...) ll __VA_ARGS__;lin(__VA_ARGS__)
#define VL(n,...) vec<ll>__VA_ARGS__;setsize({n},__VA_ARGS__);lin(__VA_ARGS__)
#define FO(n) for(ll ij=n;ij-->0;)
#define FOR(i,...) for(auto[i,i##stop,i##step]=range(0,__VA_ARGS__);i<i##stop;i+=i##step)
#define fo(i,...) FO##__VA_OPT__(R)(i __VA_OPT__(,__VA_ARGS__))
#define of(i,...) for(auto[i,i##stop,i##step]=range(1,__VA_ARGS__);i>=i##stop;i+=i##step)
#define fe(a,i,...) for(auto&&__VA_OPT__([)i __VA_OPT__(,__VA_ARGS__]):a)
#define single_testcase void solve();}int main(){my::io();my::solve();}namespace my{
void io(){cin.tie(nullptr)->sync_with_stdio(0);cout<<fixed<<setprecision(15);}
using ll=long long;
constexpr auto range(bool s,auto...a){array<ll,3>r{0,0,1};ll I=0;((r[I++]=a),...);if(!s&&I==1)swap(r[0],r[1]);r[0]-=s;if(s)r[2]*=-1;return r;}
constexpr char newline=10;
constexpr char space=32;
bool amin(auto&a,const auto&b){return a>b?a=b,1:0;}

template<class...A>ostream&operator<<(ostream&o,const tuple<A...>&t){apply([&](const auto&...a){ll i=sizeof...(a);(((o<<a<<string(--i>0,space))),...);},t);return o;}
template<class T>ostream&operator<<(ostream&o,const multiset<T>&s){fe(s,e)o<<e<<string(&e!=&*s.rbegin(),space);return o;}

template<class T>struct multiset:std::multiset<T>{
  multiset(const initializer_list<T>&a={}){fe(a,e)this->emplace(e);}
  multiset(const vector<T>&a){fe(a,e)this->emplace(e);}
};

template<class V>concept vectorial=is_base_of_v<vector<typename V::value_type>,V>;
template<class T>struct vec_attr{using core_type=T;static constexpr int d=0;};
template<vectorial V>struct vec_attr<V>{using core_type=typename vec_attr<typename V::value_type>::core_type;static constexpr int d=vec_attr<typename V::value_type>::d+1;};
template<class T>using core_t=vec_attr<T>::core_type;
template<class V>istream&operator>>(istream&i,vector<V>&v){fe(v,e)i>>e;return i;}
template<class V>ostream&operator<<(ostream&o,const vector<V>&v){fe(v,e)o<<e<<string(&e!=&v.back(),vectorial<V>?newline:space);return o;}

template<class V>struct vec:vector<V>{
  using vector<V>::vector;
  vec(const vector<V>&v){vector<V>::operator=(v);}

  template<class...A>requires(sizeof...(A)>=3)vec(A...a){const ll n=sizeof...(a)-1;ll s[n];ll i=0;((i<n?s[i++]=a:0),...);*this=make_vec(s,get<n>(tuple{a...}));}
  template<class T,ll n,ll i=0>static auto make_vec(const ll(&s)[n],T x){if constexpr(i==n-1)return vec<T>(s[i],x);else{auto X=make_vec<T,n,i+1>(s,x);return vec<decltype(X)>(s[i],X);}}

  vec&operator^=(const vec&u){this->insert(this->end(),u.begin(),u.end());return*this;}
  vec operator^(const vec&u)const{return vec{*this}^=u;}
  vec&operator+=(const vec&u){vec&v=*this;fo(i,v.size())v[i]+=u[i];return v;}
  vec&operator-=(const vec&u){vec&v=*this;fo(i,v.size())v[i]-=u[i];return v;}
  vec operator+(const vec&u)const{return vec{*this}+=u;}
  vec operator-(const vec&u)const{return vec{*this}-=u;}
  vec&operator++(){fe(*this,e)++e;return*this;}
  vec&operator--(){fe(*this,e)--e;return*this;}
  vec operator-()const{vec v=*this;fe(v,e)e=-e;return v;}
};
template<ll d,class T>struct dvec_helper{using type=vec<typename dvec_helper<d-1,T>::type>;};
template<class T>struct dvec_helper<0,T>{using type=T;};
template<ll d,class T>using dvec=typename dvec_helper<d,T>::type;
template<class...A>requires(sizeof...(A)>=2)vec(A...a)->vec<dvec<sizeof...(a)-2,remove_reference_t<decltype(get<sizeof...(a)-1>(declval<tuple<A...>>()))>>>;
vec(ll)->vec<ll>;

template<ll n,class...A>void setsize(const ll(&l)[n],A&...a){((a=vec<void*>::make_vec(l,core_t<A>{})),...);}

void lin(auto&...a){(cin>>...>>a);}

template<class T>struct kth_multiset{
  ll K;
  multiset<T>pre,suf;
  kth_multiset(ll K):K(K){}

  void emplace(T x,const auto&add,const auto&del){
    if((ll)pre.size()<K){
      pre.emplace(x);
      add(x);
      return;
    }

    auto p=prev(pre.end());
    if(x>=*p){
      suf.emplace(x);
      return;
    }

    suf.emplace(*p);
    del(*p);
    pre.erase(p);

    pre.emplace(x);
    add(x);
  }

  friend ostream&operator<<(ostream&o,const kth_multiset&s){return o<<s.pre<<": "<<s.suf;}
};

template<char c=space>void pp(const auto&...a){ll n=sizeof...(a);((cout<<a<<string(--n>0,c)),...);cout<<newline;}
single_testcase
void solve(){
  LL(N,K);
  VL(N,a);
  a=-a;
  ll su=0;
  auto add=[&](ll x){su+=x;};
  auto del=[&](ll x){su-=x;};
  kth_multiset<ll>st(K-1);
  ll ans=0;
  of(i,N,1){
    if(i&1)amin(ans,su+a[i]);
    st.emplace(a[i],add,del);
  }
  pp(-ans);
}}