Kevin Sun wants to move his precious collection of $*n*$ cowbells from Naperthrill to Exeter, where there is actually grass instead of corn. Before moving, he must pack his cowbells into $*k*$ boxes of a fixed size. In order to keep his collection safe during transportation, he won't place more than two cowbells into a single box. Since Kevin wishes to minimize expenses, he is curious about the smallest size box he can use to pack his entire collection.

Kevin is a meticulous cowbell collector and knows that the size of his $*i*$-th ($1 ≤ *i* ≤ *n*$) cowbell is an integer $*s*_{*i*}$. In fact, he keeps his cowbells sorted by size, so $*s*_{*i* - 1} ≤ *s*_{*i*}$ for any $*i* > 1$. Also an expert packer, Kevin can fit one or two cowbells into a box of size $*s*$ if and only if the sum of their sizes does not exceed $*s*$. Given this information, help Kevin determine the smallest $*s*$ for which it is possible to put all of his cowbells into $*k*$ boxes of size $*s*$.

Input

The first line of the input contains two space-separated integers $*n*$ and $*k*$ ($1 ≤ *n* ≤ 2·*k* ≤ 100 000$), denoting the number of cowbells and the number of boxes, respectively.

The next line contains $*n*$ space-separated integers $*s*_{1}, *s*_{2}, ..., *s*_{*n*}$ ($1 ≤ *s*_{1} ≤ *s*_{2} ≤ ... ≤ *s*_{*n*} ≤ 1 000 000$), the sizes of Kevin's cowbells. It is guaranteed that the sizes $*s*_{*i*}$ are given in non-decreasing order.

Output

Print a single integer, the smallest $*s*$ for which it is possible for Kevin to put all of his cowbells into $*k*$ boxes of size $*s*$.

Note

In the first sample, Kevin must pack his two cowbells into the same box.

In the second sample, Kevin can pack together the following sets of cowbells: ${2, 3}$, ${5}$ and ${9}$.

In the third sample, the optimal solution is ${3, 5}$ and ${7}$.