#include<deque>
#include<fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int v[5000005];
deque<int> d;
long long s;
int n,k,i,j,w;
int main()
{
	f>>n>>k;
	
	for(i=1;i<=n;i++)
	{
		f>>v[i];
		while(d.size()&&v[d.back()]>=v[i])
			d.pop_back();
		d.push_back(i);
		if(i>=k) 
			w+=v[d.front()];
		if(i-k+1==d.front()) 
			d.pop_front();
	}
	g<<s;
	return 0;
}