A13030 | The Parade

The Berland Army is preparing for a large military parade. It is already decided that the soldiers participating in it will be divided into $k$ rows, and all rows will contain the same number of soldiers.

Of course, not every arrangement of soldiers into $k$ rows is suitable. Heights of all soldiers in the same row should not differ by more than $1$ . The height of each soldier is an integer between $1$ and $n$ .

For each possible height, you know the number of soldiers having this height. To conduct a parade, you have to choose the soldiers participating in it, and then arrange all of the chosen soldiers into $k$ rows so that both of the following conditions are met:

- each row has the same number of soldiers,
- no row contains a pair of soldiers such that their heights differ by $2$ or more.

Calculate the maximum number of soldiers who can participate in the parade.

The first line contains one integer $t$ ( $1 \le t \le 10000$ ) — the number of test cases. Then the test cases follow.

Each test case begins with a line containing two integers $n$ and $k$ ( $1 \le n \le 30000$ , $1 \le k \le 10^{12}$ ) — the number of different heights of soldiers and the number of rows of soldiers in the parade, respectively.

The second (and final) line of each test case contains $n$ integers $c_1$ , $c_2$ , ..., $c_n$ ( $0 \le c_i \le 10^{12}$ ), where $c_i$ is the number of soldiers having height $i$ in the Berland Army.

It is guaranteed that the sum of $n$ over all test cases does not exceed $30000$ .

For each test case, print one integer — the maximum number of soldiers that can participate in the parade.