#include <iostream>
#include <queue>
using namespace std;


struct compare  
{  
 bool operator()(const int& l, const int& r)  
 {  
   return l > r;  
 }  
}; 
int main()
{
  int n, k;
  cin >> n >> k;
  int arr[250000]={0x00,};
  for(int i = 0; i<n; i++)
  {
    cin >> arr[i];
  }
  long sum = 0;
  for(int i = 0; i<=n-k; i++)
  {
    priority_queue<int> max_heap;
    priority_queue<int,vector<int>, compare> min_heap;
    for(int j = i; j<i+k; j++)
    {
      max_heap.push(arr[j]);
      if(max_heap.size()-min_heap.size() > 1)
      {
        int data =max_heap.top();
        max_heap.pop();
        min_heap.push(data);
      } 
    }
    int median = max_heap.top() < min_heap.top() ? max_heap.top() : min_heap.top();
    sum += median;
  }
  cout << sum<<endl;
  return 0;
}