#include <fstream>

using namespace std;

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

int N, K, u = -1, p, a[5000003], q[5000003];
long long sum;
int main()
{
	f >> N >> K;
	for (int i = 1; i <= N; i++) f >> a[i];
	for (int i = 1; i <= N; i++) {
		if (p <= u && q[p] <= i - K) p++;
		while (p <= u)
			if (a[q[u]] >= a[i]) u--;
			else break;
		q[++u] = i;
		if (i >= K) sum += a[q[p]];
	}
	g << sum << "\n";
	return 0;
}