#include <stdio.h>
#include <stdlib.h>
#include<iostream>
#include<fstream>
#include<assert.h>
#include<time.h>

using namespace std;


int *vect  = NULL;
int *vectT = NULL;
int n = -1;
int k = -1;

int best = -1;
int intervallo = 2;
 
void readInput() {
   ifstream fin( "input.txt" ); assert( fin );
   fin >> n;
   fin >> k;

   vect = (int*)(malloc(sizeof(int)*n));
   vectT = (int*)(malloc(sizeof(int)*n));

  for(int i = 0; i < n; i++) {
   	vect[i] = 0;
	vectT[i] = 0;
   }

   for(int i=0; i< n; i++) {
	fin >> vect[i];
   }

   fin.close();
}

void writeOutput() {
   ofstream fout( "output.txt" ); assert( fout );
   fout << best << endl;
   fout.close();
}


int maxInVectT(int size) {
	int tmp =  0;
	for (int i=0; i < size; i++) 
		if(vectT[tmp] < vectT[i]) tmp = i;
	return tmp;
}

int stampa (int size) {
	for (int i=0; i < size; i++) 
		printf("%d\t", vectT[i]);
	printf("\n");
}

void somme(int size, int a) {
	if (size > 1) {
		int tmp = maxInVectT(size);
		
		if (intervallo >= k) 
			if (best < vectT[tmp])
				best = vectT[tmp];

		for(int i = 0; i < size; i++) vectT[i] = vectT[i] + vect[i+a];	

		somme(size-1, a+1);
		intervallo++;
	}
}

int main (void) {

	readInput();

	for (int i = 0; i < n-1; i++) vectT[i] = vect[i] + vect[i+1];	

	
	somme(n-1, 2);

	printf("%d\n", best);

	writeOutput();

   return 0;
}