#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n,k,s,i,a[5000005];
deque<int> d;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++) f>>a[i];
    for(i=1;i<=n;i++)
    {

        if(i<k) d.push_back(i);
        else
        {
            while(!d.empty()&&i-d.front()>=k)
                d.pop_front();
            while(!d.empty()&&a[i]<=a[d.back()]) d.pop_back();
            d.push_back(i);
            s+=a[d.front()];

        }
    }
    g<<s;
    return 0;
}