#include <bits/stdc++.h>

using namespace std;

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

const int MAX_N = 5'000'000;

int a[MAX_N + 1];
deque<int> d;
long long s;
int n, k;

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

	/// Daca i este fixat, atunci i-k+1, ..., i
	/// Pozitia i-k este eliminata din std::deque

	s = 0;
	for (int i = 1; i <= n; i++)
	{
		if (!d.empty() && d.front() == i - k)
			d.pop_front();

		while (!d.empty() && a[i] <= a[d.back()])
			d.pop_back();
		d.push_back(i);

		if (i >= k)
			s += a[d.front()];
	}

	g << s << "\n";

	f.close();
	g.close();
	return 0;
}