#include<fstream>
#include<deque>
#include<vector>

using namespace std;

vector<int> vectorE;
deque<int> d;

int main(){
	ifstream f("deque.in");
	ofstream cout("deque.out");
	int n,k;
	f>>n>>k;
	
	long long s=0;
	
	for(int i=0;i<n;i++){
		int x=0;
		f>>x;
		vectorE.push_back(x);
	}
	k--;
	for(int i=0;i<n;i++){
		while(d.size()>0 && vectorE[i]<=vectorE[d.back()]){
			d.pop_back();
		}
		d.push_back(i);
		if(d.front()==i-k-1){
			d.pop_front();
		}
		if(i>=k){
			s+=vectorE[d.front()];
		}
		
	}
	cout<<s;
	return 0;
}