#include <bits/stdc++.h>
#define nmax 5000005
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque <int> deq;
int n,k,i,a[nmax];
long long s;
int main()
{
  f>>n>>k;
  for(i=1;i<=n;i++)
    f>>a[i];
  for(i=1;i<=n;i++)
  {
      while(deq.size()&&a[deq.back()]>=a[i])
        deq.pop_back();

      deq.push_back(i);

      if(deq.front()==i-k)
        deq.pop_front();

        if(i>=k)
            s+=a[deq.front()];
  }
g<<s;
    return 0;
}