#include<bits/stdc++.h>
using namespace std;
using ll=long long;

int main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int N,K;
	cin>>N>>K;
	vector<ll>A(N);
	for(int i=0;i<N;i++)cin>>A[i];
	priority_queue<ll,vector<ll>,greater<ll>>pq;
	ll sum=0,ans=0;
	for(int i=N-1;i>=0;i--){
		if(pq.size()<K-1){
			pq.push(A[i]);
			sum+=A[i];
		}
		else{
			if(i%2==1)ans=max(ans,A[i]+sum);
			if(pq.top()<A[i]){
				sum-=pq.top();
				pq.pop();
				sum+=A[i];
				pq.push(A[i]);
			}
		}
	}
	cout<<ans<<"\n";
}