#include <iostream>
#include <fstream>
using namespace std;
#include <deque>
#include <algorithm>

typedef long long int64;//signed long long

//int e_023_deque()
int main()
{
	char* file_name = "deque.in";
	//the inputs
	int N, K;
	int64* v;
	//read the inputs
	ifstream ifs(file_name);
	ifs>>N>>K;
	//allocates the vector for storing the numbers
	v = new int64[N];
	//read the numbers
	for (int i = 0; i < N; i++) 
	{
		ifs>>v[i];
		//cout<<v[i]<<" "<<endl;
	}
	ifs.close();

	deque<int64> K_deq;
	//insert the first K numbers 
	for (int k = 0; k < K; k++)
	{
		K_deq.push_back(v[k]);
	}
	//sort the first k numbers
	sort(K_deq.begin(), K_deq.end());

	int64 sum_of_mins = K_deq.front();
	
	//for the rest of the values
	for (int n = K; n < N; n++)
	{
		//if the element to be removed is the minimum, remove it now
		//otherwise, ignore it; it will be removed later
		if (v[n-K] == K_deq.front()) K_deq.pop_front();

		//add the new element v[n] into the sequence
		//remove all the elements higher than the current element v[n];
		while (!K_deq.empty() && K_deq.back() >= v[n]) K_deq.pop_back();
		//insert the new element into the queue
		K_deq.push_back(v[n]);
		//add the minimum to the sum of 
		sum_of_mins += K_deq.front();
	}

	ofstream ofs("deque.out");
	ofs<<sum_of_mins;
	ofs.close();

	//release the memory
	delete[] v;

	return 0;
}