#include <iostream>
#include <fstream>
#include <algorithm>
#include <vector>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long v[5000002], n, k, s;
vector<int> h;
int main()
{
   f>>n>>k;
   for(int i=0; i<n; ++i)
    f>>v[i];
   for(int i=0; i<n-k+1; ++i){
    for(int j=i; j<i+k; ++j)
        h.push_back(-v[j]);
    make_heap(h.begin(), h.end());
    s+=-h.front();
    h.clear();
   }
    g<<s;

    return 0;
}