#include <fstream>
#include <deque>

using namespace std;

ifstream fin ("deque.in");
ofstream fout ("deque.out");

#define NMAX 5000008
#define pb push_back
#define pf push_pront

int i,n,k,a[NMAX];
long long int s;
deque<int>d;


int main()
{
    fin>>n>>k;
    for (i=1; i<=n; i++)
    {
        fin>>a[i];
    }
    d.pb(1);
    for (i=2; i<=n; i++)
    {
        while (!d.empty() && a[i]<=a[d.back()])
        {
            d.pop_back();
        }
        d.pb(i);
        if (i-d.front()==k)
        {
            d.pop_front();
        }
        if (i>=k)
        {
            s+=a[d.front()];
        }
    }
    fout<<s;
    return 0;
}