#include <fstream>
using namespace std;
ofstream fout("transport.out");
ifstream fin ("transport.in" );
int n , k , v[20000] , maxi;
int main()
{
    fin>>n>>k;
    for( int i = 1 ; i <= n ; i++ ) fin>>v[ i ];
    int a = n - k;
    for( int i = 1 ; i <= a ; i++ )
    {
        int rasp = 2000000000;
        int cnt = 0;
        for( int j = 2 ; j <= n ; j++ )
        {
            if( v[ j ] + v[ j - 1 ] < rasp )
            {
                rasp = v[ j ] + v[ j - 1 ];
                cnt = j;
            }
        }
        v[ cnt - 1 ] = v[ cnt ] + v[ cnt - 1 ];
        n--;
        for(int i = cnt ; i <= n ; i++) v[ i ] = v[ i + 1 ];
    }
    for( int i = 1 ; i <= n ; i++ ) maxi = max( maxi , v[ i ] );
    fout<<maxi;
}