#include <iostream>
using namespace std;
const int N = 1000010;
long long a[N], n, k, s, ma;
int main()
{
	cin >> n >> k;
	for (int i = 1; i <= n; i++)
    {
		cin >> a[i];
		s += a[i];
		a[i] += a[i-1];
		if (i >= k)
			ma = max(ma, a[i] - a[i - k]);
	} 
	cout << s - ma;
	return 0;
}