#include <bits/stdc++.h>

const int inf=2e9;
const int nmax=2e5;

using namespace std;

int main()
{
  ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
  freopen("deque.in","r",stdin);
  freopen("deque.out","w",stdout);

  long long n,k;
  cin>>n>>k;
  deque<int>q;
  vector<long long>v(n+3);
  long long sum=0;
  for(int i=1;i<=n;i++)
  {
    cin>>v[i];
    while(!q.empty() && v[i]<v[q.back()]) q.pop_back();
    q.push_back(i);
    if(q.front()<=i-k) q.pop_front();
    if(i>=k) sum+=v[q.front()];
  }
  cout<<sum;
}