#include <fstream>

int main() {
	std::ifstream fin("deque.in");
	std::ofstream fout("deque.out");

	int n, k;
	long long s = 0;
	int* v = new int[5000000] {0};
	int vb = 0, ve = 0;
	fin >> n >> k;

	int cn = n;
	while (cn--) {
		int nr;
		fin >> nr;

		v[ve] = nr;
		while (vb < ve and v[vb] >= v[ve] or ve - vb >= k) {
			++vb;
		}
		if (n - cn >= k) {
			s += v[vb];
		}
		++ve;
	}
	fout << s << "\n";

	delete[] v;
	return 0;
}