#include <fstream>
#include <deque>

using namespace std;

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

int n, k, a[5000001], s;
deque <int> d;

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