Statement : F. Load Unbalancing
Note the unusually low time limit.
You are given a sequence $a$ of length $n$, as well as an integer $k$.
You may first reorder the elements of $a$ however you like. Then, define $f(a)$ as follows:
- Let $b$ be an array of length $k$ which is initially all zeros.
- For each $1 \le i \le n$ in order, add $a_i$ to any minimum element of $b$.
- At the end of this process, $f(a) = \max(b)$.
Find the maximum possible value of $f(a)$ among all rearrangements of $a$.
Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 10^4$). The description of the test cases follows.
The first line of each test case contains two integers $n$ and $k$ ($1 \le k \le n \le 18$).
The second line of each test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le 10^9$).
It is guaranteed that the sum of $2^n$ over all test cases does not exceed $2^{18}$.
For each test case, output a single integer — the maximum possible value of $f(a)$ among all rearrangements of $a$.
Input
1
18 5
837492015 264819073 519603847 902746518 173058264 648291507 395174620 781532946 506847193 924613708 158397042 673029415 240785631 819456270 461302987 730619824 528947163 894271056
Output
2823249283
Note
In the first test case of the second example, one optimal rearrangement of $a$ is $[1, 4, 2, 5]$. $f(a)$ is computed as follows:
$i$$a_i$$b$$-$$-$$[0, 0]$$1$$1$$[1, 0]$$2$$4$$[1, 4]$$3$$2$$[3, 4]$$4$$5$$[8, 4]$
After this, $f(a) = \max([8,4]) = 8$. It can be shown that the maximum achievable $f(a)$ is $8$.
In the third test case of the second example, one optimal rearrangement of $a$ is $[3, 1, 2, 3, 5, 4, 3, 4]$.