#include <fstream>
#include <deque>


using namespace std;

    ifstream cin("deque.in");
    ofstream cout("deque.out");

    const int dim = 5e6 + 5;
    deque<int> q;
    int v[dim];

   int main() {

    int n, k, i, j, x;
    long long int s = 0;

    cin >> n >> k;

    for (i = 1; i <= n; ++i)
        cin >> v[i];

    for (i = 1; i <= n; ++i) {

        while (!q.empty() && v[q.back()] >= v[i])
            q.pop_back();

        q.push_back(i);

        if (q.front() == i - k)
            q.pop_front();

        if (i >= k)
            s += v[q.front()];

    }

    cout << s;
    return 0;
}