#include <fstream>
#include <deque>
#include <vector>
using namespace std;

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

int a[5000005];
int n, k, x;

void cu_deque()
{
	long long s = 0;
	deque<int> d;
	for (int i = 1; i <= n; i++)
	{
		f >> x;
		a[i] = x;
		while (!d.empty() && x <= a[d.back()])
			d.pop_back();
		d.push_back(i);
		if (i >= k)
		{
			while (i - d.front() >= k)
				d.pop_front();
			s += a[d.front()];
		}
	}
	g << s;
}

int main()
{
	f >> n >> k;
	cu_deque();
	return 0;
}