#include<bits/stdc++.h>
using namespace std;


int main(){
	ifstream f("deque.in");
	ofstream f1("deque.out");
	int n,k;
	f>>n>>k;
	int v[n],deq[n],suma=0;
	for (int i=1;i<=n;i++)
		f>>v[i];
	
	int st=1,dr=1;
	
	deq[1]=1;
	
	for (int i=2;i<=n;i++){
		
		while (st<=dr && v[deq[dr]]>=v[i])
			dr--;
		dr++;
		deq[dr]=i;
		
		if (deq[st]<=i-k)
			st++;
		if (i>k-1)
			suma+=v[deq[st]];
	}
	f<<suma;
	
}