#include <fstream>
#include <deque>
using namespace std;
int v[5000005];
deque <int> dq;
int main()
{
    ifstream fin("deque.in");
    ofstream fout("deque.out");

    int n, k;
    long long s = 0;
    fin >> n >> k;
    for (int i = 1; i <= n; i++) fin >> v[i];
    dq.push_back(1);
    for (int i = 2; i <= n; i++)
    {
        while (!dq.empty() && v[i] <= v[dq.back()]) dq.pop_back();
        dq.push_back(i);
        if (i - dq.front() == k) dq.pop_front();
        if (i >= k) s += v[dq.front()];
    }

    fout << s;
    return 0;
}