#include<bits/stdc++.h>
using namespace std;

int i,n,k,deq[5000005],st=1,dr,a[5000005];
long long rs;

int main()
{
  ifstream cin("deque.in");
  ofstream cout("deque.out");

  ios_base::sync_with_stdio(0);

  cin>>n>>k;
  for(i=1;i<=n;++i) cin>>a[i];

  for(i=1;i<=n;++i)
  {
    while(st<=dr && a[i]<=a[deq[dr]]) --dr;
    deq[++dr]=i;
    if(deq[st]<=i-k) ++st;
    if(i>=k) rs+=a[deq[st]];
  }

  cout<<rs<<'\n';

 return 0;
}