#include <iostream>
#include <algorithm>
#include <iterator>
#include <string>
#include <math.h>
#include <vector>
#include <set>
#include <map>
using namespace std;
long long a[100001];
int main() {
	int n, k, p;
	long long s, sum, ans = 0;
	cin >> n >> k;
	for (int i = 0; i < n; i++) {
		cin >> a[i];
		ans += a[i];
	}
	p = 0;
	s = ans;
	while (p < n) {
		sum = 0;
		for (int i = 0; i < n && p + (i * k) < n; i++) {
			sum += a[p + (i * k)];
		}
		sum = s - sum;
		ans = min(ans, sum);
		p++;
	}
	cout << ans;
	return 0;
}