#include <iostream>
#include <fstream>

using namespace std;

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

const long long N = 5000000;
long long s;

int main()
{
	int k, dq[N], v[N];
	int st = 0, dr = -1;
	for (int i = 0; i < N; i++) {
		in >> v[i];
	}
	for (int i = 0; i < N; i++) {
		if (st <= dr && dq[st] == i - k) {
			st++;
		}
		while (st <= dr && v[i] <= v[dq[dr]]) {
			dr--;
		}
		dq[++dr] = i;
		if (i = k - 1) {
			s += v[dq[st]];
		}
	}
	out << s;
	return 0;
}