#include <fstream>
#include <deque>
using namespace std;
ifstream cin ("deque.in");
ofstream cout ("deque.out");
deque <int> dq;
int v[5000005];
int main()
{
    int n, k, nr, i;
    long long s = 0;
    cin >> n >> k;
    for (i = 1; i <= n; i++)
    {
        cin >> v[i];
        while (!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)
            s += v[dq.front()];

    }
    cout << s;
    return 0;
}