#include <fstream>

using namespace std;

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

int arr[5000001], deq[5000001];
int  n, k, st, dr;
long long s;

int main() {
    f >> n >> k;
    for (int i = 1; i <= n; i++)
    {
        f >> arr[i];
        //g<<arr[i]<<" ";
    }
    for (int i = 1; i <= n; i++) {
        while (st <= dr && arr[i] <= arr[deq[dr]])
            dr--;
        deq[++dr] = i;
        if (deq[st] <= i - k)
            st++;
        if (i >= k)
            s += arr[deq[st]];
    }
    g << s;
    return 0;
}