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#include <fstream>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
#define int long long 
deque<int>filip;
int v[5000005];
signed main()
{
    int n,k,a,sum=0;
    cin>>n>>k;
  // start=1;
    for(int i=1;i<=n;i++)
    {
        cin>>v[i];
    
    }
    for(int i=1;i<=n;i++)
    {
        while(filip.empty()==false && v[i]<v[filip.back()])
        {
            filip.pop_back();
        }
        while(filip.empty()==false && filip.front()<=i-k)
        {
            filip.pop_front();
        }
        filip.push_back(i);
        if(i>=k)
        {
            sum+=v[filip.front()];
          //  cout<<filip.front()<<" ";
        }
    }
   cout<<sum;

    return 0;
}