#include <fstream>
#include <deque>

using namespace std;

int numbers[5000001];

long long minSum(deque<int>& noSequence,
                 int N,
                 int K) 
{
    long long s = 0;
    for (int i = 1; i <= N; i++) {

        /* while the current value is smaller than the values
            from the end of the deque, we no longer need them */
        while (!noSequence.empty() &&
                numbers[i] <= numbers[noSequence.back()]) {
            noSequence.pop_back();
        }

        noSequence.push_back(i);
        // cout << noSequence.back() << '\n';

        /* check if the current min value is no longer needed */
        if (noSequence.front() == i - K) noSequence.pop_front();

        /* compute the minSum */
        if (i >= K) {
            s += numbers[noSequence.front()];
        } 
    }
    return s;
}

int main()
{
    ifstream in("deque.in");
    ofstream out("deque.out");

    int N, K;
    in >> N >> K;

    for (int i = 1; i <= N; i++) 
        in >> numbers[i];

    deque<int>noSequence;
    out << minSum(noSequence, N, K);

    in.close();
    out.close();

    return 0;
}