#include<iostream>
#include<vector>
#include<fstream>
#include<deque>
#include<list>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int main()
{
	int n, k;
	long Sum = 0;;
	f >> n >> k;
	vector<int> v(n + 1);
	deque<int> q;
	for (int i = 1; i <= n; i++)
		f >> v[i];
	for (int i = 1; i <= n; i++)
	{
		while (!q.empty() && v[i] <= v[q.back()])
			q.pop_back();
		q.push_back(i);
		if (q.front() <= i - k)
			q.pop_front();
		if (i >= k)
			Sum += v[q.front()];
	}
	g << Sum;
}