#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int>d;
int n,i,k,v[5000005];
long long s;
int main()
{
   f>>n>>k;
   for(i=1;i<=n;i++)
   {
       f>>v[i];
       while(!d.empty()&&v[d.back()]>=v[i]) d.pop_back();
       d.push_back(i);
       if(i-d.front()==k)d.pop_front();
       if(i>=k)s=s+v[d.front()];
   }
  cout<<s;
    return 0;
}