#include <fstream>
#include <algorithm>
using namespace std;
int v[16001];
ifstream cin("transport.in");
ofstream cout("transport.out");
int sume[100000];
int main()
{
    int sum=0,sumx=-1,j,n,k,i;
    cin>>n>>k;
    for(i=1;i<=n;++i)
    {
        cin>>v[i];
    } sort(v+1,v+n+1); j=n;
    for(i=1;i<=n/2 && k>=2;++i)
    {k--;
    if(v[i]+v[j]>sumx)
    sumx=v[i]+v[j];
    j--;
    }
    if(k==1)
    {
        while(i<=n/2 && j>n/2)
        {
            sum+=v[i]+v[j];
            i++;
            j--;
        }
        if(sum>sumx)
        sumx=sum;
    }
    cout<<sumx;
    return 0;
}