#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;
}

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

NiA0IAotMyA0IDMgLTIgMiA1IA==

6 4 
-3 4 3 -2 2 5