#include <bits/stdc++.h>

using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");

const int NMAX=5000005;

int N,K;
long long a[NMAX],S;
deque <int> d;

int main()
{
	
	fin >> N >> K;
	
	for(int i=1;i<=N;i++)
	    fin >> a[i];
	    
	for(int i=1;i<=N;i++)
	{
		while(!d.empty() and a[i]<=a[d.back()])
		    d.pop_back();
		d.push_back(i);
		if(d.front()==i-K)
		    d.pop_front();
		if(i>=K)
		    S+=a[d.front()];
	}
	
	fout << S;
	
	return 0;
	
}