| # P1012 Concatenating Numbers | |
| ## Abstract model | |
| Treat every positive integer as a decimal string. Find a permutation whose | |
| concatenation is lexicographically, and therefore numerically, greatest. | |
| Ordering strings $x$ and $y$ by whether $xy>yx$ yields an optimal arrangement. | |
| This case verifies the comparison-sort implementation. | |
| ## Problem statement | |
| Given $n$ positive integers, arrange all of them in one row and concatenate | |
| adjacent decimal representations. Output the largest integer that can be | |
| formed. | |
| ## Input and output | |
| The first line contains $n$. The second line contains $n$ positive integers. | |
| Output their maximum possible concatenation without separators. | |
| ## Constraints | |
| - $1 \le n \le 20$. | |
| - $1 \le a_i \le 10^9$. | |
| ## Source | |
| [Luogu P1012, NOIP 1998 Senior, Problem 2](https://www.luogu.com.cn/problem/P1012). | |