#include <iostream>
#include <fstream>
#include <deque>

using namespace std;

deque<int>dq;

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

int arr[5000000 + 8];

int main()
{
	int n,a, k, rez=0;
	fin >> n >> k;
	for (int i = 1; i <= n; i++)
	{
		fin >> a;
		arr[i] = a;
		if (dq.empty()) dq.push_back(a);
		else
		{
			while (!dq.empty())
			{
				if (dq.back() > a)dq.pop_back();
				else break;
			}
			dq.push_back(a);

		}
		if (i >= k) {
			if (i > k)
			{
				if (arr[i - k] == dq.front()) dq.pop_front();
			}
			rez += dq.front();
		}
	}

	fout << rez;

	return 0;
}