#include <deque>
#include <fstream>
using namespace std;

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

deque <int> d;
deque <int>::iterator it;
int v[5000000], n, k, sum=0;

void read()
{
	in >> n >> k;
	for (int i=1; i<=n; i++)
		in >> v[i];
}

void deq()
{
	for (int i=1; i<=n-k+1; i++)
	{
		if (d.empty())
		{
			d.push_back(v[i]);
			it=d.begin();
		}
		for (int j=i; j<=k+i-1; j++)
		{
			if (v[j]<*it)
			{
				d.push_front(v[j]); 
				it=d.begin();
				d.pop_front();
			}
		}
		sum+=*it;
		if (*it=v[i])
			d.pop_back();
	}
}

int main()
{
	read();
	deq();
	out << sum;
}