#include <iostream>
#include <fstream>
#include <deque>
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");
long long int n,nr=0;
int v[5000005],k;
deque < int > coada;
int main()
{
cin>>n>>k;
for(int i=1;i<=n;i++)
  cin>>v[i];
for(int i=1;i<=n;i++)
  {
   while( !coada.empty() && v[i]<=v[coada.back()] )
      coada.pop_back();
   coada.push_back(i);
   if( coada.front() == i-k ) coada.pop_front();
   if( i>=k ) nr+=v[coada.front()];
  }
cout<<nr;
}