#include <fstream>
#include <deque>

using namespace std;
ifstream cin ("deque.in");
ofstream cout ("deque.out");
const int dim = 5e6 + 5;

int v[dim];
deque<int> dq;

int main()
{
    int n  , k;
    long long sum = 0;
    cin >> n >> k;
    for(int i = 1 ; i <= n ; ++i)
        cin >> v[i];
    for(int i = 1 ; i <= n ; ++i)
        {
            while(!dq.empty() && v[i] <= v[dq.back()])
                dq.pop_back();
            dq.push_back(i);
            if(i - dq.front() >= k)
                dq.pop_front();
            if(i >= k)
                sum += v[dq.front()];
        }
    cout << sum;
}