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


const char iname[] = "deque.in";
const char oname[] = "deque.out";

int main() {
	ifstream in(iname);
	ofstream out(oname);
	int n, k, i, v[6000001];
	in >> n >> k;
	int minim, suma = 0;
	for (i = 0; i < n; i++) {
		in >> v[i];
		if (i >= k - 1) {
			minim = v[i];
			for (int j = i; j > i - k; j--) {
				if (v[j] < minim)
					minim = v[j];
			}
			suma += minim;
		}
	}
	out << suma;
	return 0;
}