#include <cstdio>
#include <deque>

const int NMAX = 5000005;
int n, k, a[NMAX];
long long result;

int main() {
	freopen("deque.in", "r", stdin);
	freopen("deque.out", "w", stdout);

	scanf("%d %d", &n, &k);
	for (int i = 1; i <= n; i++)
		scanf("%d", &a[i]);

	std::deque<int> d;

	for (int i = 1; i <= n; i++) {
		if (d.front() == i - k)
			d.pop_front();

		while (!d.empty() && a[d.back()] > a[i])
			d.pop_back();

		d.push_back(i);

		result += (i >= k ? a[d.front()] : 0);
	}


	printf("%lld\n", result);

	return 0;
}