#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque<int> q;
int n,x,s,v[5000005],i,k;
int main()
{ fin>>n>>k;
  for(i=1;i<=n;i++)
  {fin>>v[i];
   if(q.empty())
      q.push_front(i);
   while(i-q.front()>=k)  q.pop_front();
   while(v[i]<v[q.back()])
   {q.pop_back();
    if(q.empty()) break;
   }
   q.push_back(i);
   if(i>=k)
   s+=v[q.front()];
  }
  fout<<s;
    return 0;
}