输入格式

The first line of the standard input holds two integers and (, ), separated by a single space, that denote the number of Byteasar's hamsters and the minimum number of occurrences of the hamsters' names on the display.

Each of the following lines contains a non-empty string of non-capital letters of the English alphabet that is the hamster's name.

The total length of all names does not exceed letters.

最关键的字符串总长度最大值没搬过来，最大值还没人翻译，全都闭口不谈。我非常不喜欢盲开 trie 大小。