#include <fstream>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
deque<int> mi;
int a[5000001],n,k,s;

int main()
{
    cin>>n>>k;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        while(!mi.empty()&&a[mi.front()]>=a[i])
            mi.pop_front();
        mi.push_front(i);
        if(mi.back()==i-k) {mi.pop_back();}
        if(i>=k) s=s+a[mi.back()];


    }
  cout<<s;
    return 0;
}