#include <bits/stdc++.h>
using namespace std;
int a[3005];
int minn=200000000;
int main()
{
	int n,m;
	cin>>n>>m;
	for(int i=0;i<n;i++)cin>>a[i];
	for(int i=0;i<n-m;i++)
	{
		int k=0;
		for(int j=i;j<=i+m-1;j++)
			k+=a[j];
		minn=min(minn,k);
	}
	cout<<minn;
	return 0;
 } 

谢谢各位大佬！