#include <fstream>
#include <deque>
#define N  5000010
using namespace std;

ifstream f ("deque.in");
ofstream g ("deque.out");

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

int main()
{
    int n, k, i, a;
    long long int suma;
    suma = 0;

    f >> n >> k;
    for (int i = 1; i <= n ; ++i)
        f >> v[i];

    for (i = 1; i <=k; ++i)
    {
        while (!dq.empty() && v[dq.back()] > v[i])
            dq.pop_back();
        dq.push_back(i);
    }

    for (i = k + 1; i <= n; ++i)
    {
        a = dq.front();
        suma += v[a];

        if (i - k >= a)
            dq.pop_front();

        while (!dq.empty() && v[dq.back()] > v[i])
            dq.pop_back();
        dq.push_back(i);
    }

    suma += v[dq.front()];
    g << suma;
    return 0;
}