#include <iostream>
using namespace std;
int main()
{
	int i, j,m, n,k, a[100], x,t=0, min = 0;
	cin >> n >> m;
	for (i = 0;i < n;i++)
	{
		cin >> a[i];
	}
	for (j = 0;j < m;j++)
		min += a[j];
		for (i = 0;i < n-m+1;i++)
		{
			k = i;
			for (j = i;j < k+m;j++)
				t += a[j];
			if (min > t) min = t, t = 0;
		    else t=0;
		}
		cout << min;
	return 0;
}