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

int n, k, v[5000000], deque[5000000], L = 0, R = -1;
long long s;

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

int main()
{
	fin >> n >> k;
	for (int i = 0; i < n; i++)
		fin >> v[i];

	for (int i = 0; i < n; i++)
	{
		while (L <= R && v[deque[R]] >= v[i])
			R--;

		R++;
		deque[R] = i;


		if (i >= k - 1)
		{

			if (deque[L] <= i - k)
				L++;

			s += v[deque[L]];
		}
	}

	fout << s;
}