#include <fstream>
#include <stack>
#include <queue>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <set>
#include <cstring>
#include <map>
#include <string>
#include <bitset>
#include <unordered_map>
#include <unordered_set>
#define oo 2000000
#define MOD 1000000007
using namespace std;

ifstream fin("deque.in");
ofstream fout("deque.out");
int n, k,a[5000001];
deque<int>q;
long long s;
int main()
{
	fin >> n >> k;
	for (int i = 1; i <= n; i++)
		fin >> a[i];
	for (int i = 1; i <= n; i++)
	{
		while (!q.empty() &&  a[q.back()] >= a[i])
			q.pop_back();
		q.push_back(i);
		if ( q.front() <= i - k)
			q.pop_front();
		if (i >= k)
			s += a[q.front()];
	}
	fout << s;


}