#include <fstream>
#include <deque>

using namespace std;

int n, k;

int v[5000002];

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

int main()
{
	fin >> n >> k;
	for(int i = 1; i <= n; ++i)
		fin >> v[i];
	
	deque<int> d;
	
	long long ans = 0;
	for(int i = 1; i <= n; ++i)
	{
		if(!d.empty() && i - d.front() == k)
			d.pop_front();
		while(!d.empty() && v[i] <= v[d.back()])
			d.pop_back();
		d.push_back(i);
		if(i >= k)
			ans += v[d.front()];
	}
	
	fout << ans << '\n';
	return 0;
}