#include<fstream>
#include<deque>
#define dim 5000032

using namespace std;


ifstream f("deque.in");
ofstream g("deque.out");
int n,k,a[dim];
long long suma;
void solve(){
	deque<	int  >w;
	
	
	for(int i=1;i<=n;++i){
		while(!w.empty() && a[w.back()]>=a[i])
			w.pop_back();
		w.push_back(i);
		if(i-w.front()==k){
			w.pop_front();
		}
		if(i>=k){
			suma+=a[w.front()];
		}
	}
	
	g<<suma<<"\n";
}
int main ( ) {
	
	
	f>>n>>k;
	
	for(int i=1;i<=n;++i){
		f>>a[i];
	}
	
	solve();

	return 0;
	
	
}