#include <fstream>
#include <deque>

using namespace std;

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

long long n, k, v[5000001], sol;

deque <int> dq;

int main()
{
    cin >> n >> k;

    for (int i = 1; i <= n; i++)
    {
        cin >> v[i];
        while (!dq.empty() && v[dq.front()] >= v[i])
        {
            dq.pop_front();
        }
        dq.push_front(i);
        while (!dq.empty() && i - dq.back() + 1 > k)
        {
            dq.pop_back();
        }
        if (!dq.empty() && i >= k)
        {
            sol += v[dq.back()];
        }
    }
    cout << sol << '\n';

    return 0;
}