#include <fstream>
#include <deque>

using namespace std;

ifstream cin("deque.in");
ofstream cout("deque.out");

#define MAXN 5000000

int v[MAXN + 1];
deque<int> dq;

int main()
{
    int n, k;
    cin >> n >> k;
    int i;
    long long sum = 0;
    for(i = 1; i <= n; i++)
    {
        cin >> v[i];
        while(dq.empty() != true && v[dq.back()] >= v[i])
            dq.pop_back();

        dq.push_back(i);

        if(dq.front() <= i - k)
            dq.pop_front();

        if(i >= k)
            sum += v[dq.front()];
    }
    cout << sum;
}