#include <fstream>
#include <deque>
using namespace std;
deque <pair<int,int>> dq;
ifstream cin("deque.in");
ofstream cout("deque.out");
int main()
{
    int n, k;
    cin >> n;
    cin >> k;
    int x;
    long long s=0;
    for (int i = 1; i <= n; i++)
    {
        cin >> x;
        while (!dq.empty() && dq.back().first >= x)
        {
            dq.pop_back();
        }
        dq.push_back(make_pair(x, i));
        while (!dq.empty() && dq.front().second <= i - k)
        {
            dq.pop_front();
        }
        if (i >= k)
            s += dq.front().first;
    }
    cout << s;
    return 0;
}