Get Latest K Requests

After receiving all requests, output the most recent k distinct request IDs, ordered from most recent to least recent by the last time each ID appeared. The original example makes clear that a repeated ID is reported only once. If there are fewer than k distinct IDs, this site's output convention is -1.

输入格式

The first line contains n k, followed by n lines of request IDs. On this site 1≤n,k≤100000, and each ID consists of 1 to 20 non-newline Unicode scalar characters and may contain spaces; read input line by line without trimming spaces.

输出格式

If there is no solution, output only -1; otherwise output k on the first line, followed by k lines of request IDs from most recent to least recent, with spaces preserved.

样例 1

输入：

5 3
item1
item2
item3
item1
item3

输出：

3
item3
item1
item2

样例 2

输入：

2 2
a
a

输出：

-1

样例 3

输入：

3 2
a b
 a 
a b

输出：

2
a b
 a 

样例说明

The examples output, line by line, 3, item3, item1, item2; -1; and 2, a b, a surrounded by spaces, respectively.