#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque<int> q;
int n,x,v[5000005],i,k;
long long s;
int main()
{ fin>>n>>k;
  for(i=1;i<=n;i++)
  {fin>>v[i];
   if(q.empty())
      q.push_front(i);
   if(i-q.front()==k)  q.pop_front();
   while(!q.empty() &&v[i]<=v[q.back()])
   {q.pop_back();

   }
   q.push_back(i);
   if(i>=k)
   s+=v[q.front()];
  }
  fout<<s;
    return 0;
}