#include <fstream>
#include <deque>

using namespace std;

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

const int N = 5000000;

int n, k, v[N];
deque <int> dq;

int main()
{
    long long s = 0;
    in >> n >> k;
    for (int i = 0; i < n; i++) {
        in >> v[i];

        if (!dq.empty() && dq.front() == i - k) dq.pop_front();

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

        if (i >= k - 1) s += v[dq.front()];
    }
    out << s;
}