#include <fstream>
#include <deque>
using namespace std;
ifstream f ("deque.in");
ofstream g ("deque.out");

int N, K, v[5000001];
long long suma;
deque <int> deq;
int main()
{
    f >> N >> K;
    for (int i = 1; i <= N; i++)
    {
        f >> v[i];
        while (!deq.empty() && v[deq.back()] >= v[i])
            deq.pop_back();
        deq.push_back (i);
        if (deq.front() == i - K)
            deq.pop_front();
        if (i >= K)
            suma += 1LL * v[deq.front()];
    }
    g << suma;
    return 0;
}