#include <fstream>
#include <deque>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> deq;
long long v[5000001],s,n,k,i;
int main()
{
    fin>>n>>k;
    for (i=1;i<=n;i++)
    {
        fin>>v[i];
        while (!deq.empty() && v[deq.back()]>=v[i])
            deq.pop_back();
        deq.push_back(i);
        if (deq.front()==i-k)
            deq.pop_front();
        if (i>=k)
            s+=v[deq.front()];
    }
    fout<<s;
        return 0;
}