#include<cstdio>
#include<queue>
#include<algorithm>
#include<cstring>
#include<vector>
using namespace std;
priority_queue<int,vector<int>,greater<int> > pq;
int n,m;
int a,ans=0;
void read(){
	scanf("%d%d",&n,&m);
	for (int i=1;i<=m;i++){
		scanf("%d",&a);
		pq.push(a);
		ans=max(a,ans);
	}
	for (int i=m+1;i<=n;i++){
		scanf("%d",&a);
		int t=pq.top();
		pq.pop();
		pq.push(t+a);
		ans=max(ans,t+a);
	}
	printf("%d",ans);
}
int main(){
	freopen("waterj.in","r",stdin);
	freopen("waterj.out","w",stdout);
	read();
}