#include<bits/stdc++.h>
using namespace std;
int main(){
int  n,m,a[10000],sum=0,minn=10000;
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	for(int i=1;i<=n-m+1;i++){
		sum=0;
		for(int j=i;j<=i+m-1;j++){
			sum+=a[j];
		}
		minn=min(minn,sum);
	}
	cout<<minn;
}