#include <fstream>
#include <deque>

using namespace std;

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

const int LMAX = 5e6 + 10;
int v[LMAX];

deque <int> d;

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