#include <fstream>

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

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

	long long cn = n;
	while (cn--) {
		long long 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;
}