#include <iostream>
#include <fstream>
#include <stdio.h>
using namespace std;



int main() {
	freopen("deque.in", "r", stdin);
	freopen("deque.out", "w", stdout);

	int n, k, i, v[60001];
	scanf("%d %d ", &n, &k);
	int minim, suma = 0;
	for (i = 0; i < n; i++) {
		scanf("%d ", &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;
		}
	}
	printf("%lld\n", suma);
	return 0;
}