#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int n, v[5000010], k, d[5000010], i, sum, u, p;
int main(){
	f>>n>>k;
	for(i=1; i<=n; i++)
	{
		f>>v[i];
		
	}
	
	
	p=u=1;
	d[1]=1;
	for(i=2; i<=n; i++)
	{
		while(p<=u && v[i]<v[ d[u] ])
			u--;
		d[++u]=i;
		if(d[p]<=i-k)
			p++;
		if(i>=k)
			sum+=v[ d[p] ];
	}
	g<<sum<<"\n";
	return 0;
}