AT_abc394_b [ABC394B] cat

You are given $ N $ strings $ S_1, S_2, \ldots, S_N $ , each consisting of lowercase English letters. The lengths of these strings are all distinct. Sort these strings in ascending order of length, and then concatenate them in that order to form a single string.

The input is given from Standard Input in the following format: > $ N $ $ S_1 $ $ S_2 $ $ \vdots $ $ S_N $

Print the answer.

### Sample Explanation 1 When we sort (`tc`, `oder`, `a`) in ascending order of length, we get (`a`, `tc`, `oder`). Concatenating them in this order yields the string `atcoder`. ### Constraints - $ 2 \leq N \leq 50 $ - $ N $ is an integer. - Each $ S_i $ is a string consisting of lowercase English letters with length between $ 1 $ and $ 50 $ , inclusive. - If $ i \neq j $ , the length of $ S_i $ is different from the length of $ S_j $ .