#include <fstream>
#include <deque>
using namespace std;

const int NM = 5e6;
int v[NM];

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

int main()
{
    int n, k;
    fin >> n >> k;
    long long s = 0;
    deque<int> deq;
    for (int i = 0; i < n; ++i) {
        fin >> v[i];
        while (!deq.empty() && v[deq.front()] >= v[i])
            deq.pop_front();
        deq.push_front(i);
        while (!deq.empty() && i - deq.back() >= k)
            deq.pop_back();
        if (i >= k - 1)
            s += v[deq.back()];
    }
    fout << s << '\n';
    return 0;
}