#include <fstream>
#include <list>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");

list <int> v;
int a[5000002];
int main()
{
	
	int n,k,i;
	long long s=0;
	f>>n>>k;
	for(i=1;i<=n;i++)
		f>>a[i];
	for(i=1;i<=n;i++)
	{
		while(a[i]<=a[v.back()] && !v.empty()) v.pop_back();
		v.push_back(i);
		if(v.front()==i-k) v.pop_front();
		if(i>=k) s+=a[v.front()];
	}
	g<<s<<'\n';
	
}