#include <fstream>
#include <deque>
#include <vector>
#define ll long long

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");

deque<ll> dq;
ll n, k, s, a[5000000];

void add() {
	ll x;
	fin >> x;
	while (!dq.empty() && dq.back() >= x)
		dq.pop_back();
	dq.push_back(x);
}

int main() {
	fin >> n >> k;
	int i = 0;
	for (; i < k;add(),i++);
	s += dq.front();
	for (; i < n; dq.pop_front(), add(), s += dq.front(), i++);
	fout << s;
	return 0;
}