#include<fstream>
#include<deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
deque<int> d;

int n,k,a[5000001];
long long s;
int main()
{
    int i;
    cin>>n>>k;
    for(i=1;i<=n;i++)
    cin>>a[i];
    
    for(i=1;i<=n;i++)
  {
                     while(!d.empty() && a[i]<a[d.back()])
                     d.pop_back();
                     d.push_back(i);
                     if(i-k==d.front())
                     d.pop_front();
                     if(i>=k)
                     s=s+a[d.front()];
}
  cout<<s;
  return 0;}