#include <fstream>
#include <deque>
#include <vector>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,x;
long long sum;
vector < int > v;
deque < int > coada;
int main()
{
    f>>n>>k;
    for(int i=0;i<n;i++)
      {
          f>>x;
          v.push_back(x);
      }
    for(int i=0;i<n;i++)
    {
        while(!coada.empty() && v[i]<=v[coada.back()])
            coada.pop_back();
        coada.push_back(i);
        if(coada.front()==i-k)
            coada.pop_front();
        if(i+1>=k)
            sum+=v[coada.front()];
    }
    g<<sum;
}