#include <bits/stdc++.h>
using namespace std;

int main() {
	int n,k ;cin>>n>>k;
	vector<int>a(n+1);
	
	for(int i = 1;i <= n ;i++){
		cin>>a[i];
	}
	vector<int>p(n+1,0);
	for(int i = 1 ;i<=n;i++){
		p[i]=p[i-1]+a[i];
	}
	multiset<int>u;
	int r = 0;
	int final = 0;
	for(int i = 1 ; i<=n ;i++){
		if(u.size()>k){
			u.erase(u.find(p[i-k-1]));
		}
		
		r = p[i]-*u.begin();
		final = max(final,r);
		u.insert(p[i]);
	}
	cout<<final;
	return 0;
}