Description

Input

The first line of the input contains integer numbers $n$ and $k$ ($1 \le n \le 2 \cdot 10^5$, $0 \le k \le n$). The second line of the input contains $n$ integer numbers $a_1, a_2, \dots, a_n$ ($1 \le a_i \le 10^9$) — the sequence itself.

Output

Print any integer number $x$ from range $[1; 10^9]$ such that exactly $k$ elements of given sequence is less or equal to $x$.

If there is no such $x$, print "-1" (without quotes).

7 4
3 7 5 1 10 3 20

6

7 2
3 7 5 1 10 3 20

-1

Note

In the first example $5$ is also a valid answer because the elements with indices $[1, 3, 4, 6]$ is less than or equal to $5$ and obviously less than or equal to $6$.

In the second example you cannot choose any number that only $2$ elements of the given sequence will be less than or equal to this number because $3$ elements of the given sequence will be also less than or equal to this number.