CF1906A.Easy As ABC

You are playing a word puzzle. The puzzle starts with a $3$ by $3$ grid, where each cell contains either the letter A, B, or C.

The goal of this puzzle is to find the lexicographically smallest possible word of length $3$. The word can be formed by choosing three different cells where the cell containing the first letter is adjacent to the cell containing the second letter, and the cell containing the second letter is adjacent to the cell containing the third letter.

Two cells are adjacent to each other if they share a border or a corner, as shown in the following illustration. Formally, if $(r, c)$ denotes the cell in the $r$-th row and $c$-th column, then cell $(r, c)$ is adjacent to cell $(r, c + 1)$, $(r - 1, c + 1)$, $(r - 1, c)$, $(r - 1, c - 1)$, $(r, c - 1)$, $(r + 1, c - 1)$, $(r + 1, c)$, and $(r + 1, c + 1)$.

Determine the lexicographically smallest possible word of length $3$ that you can find within the grid.

A string $s$ of length $n$ is lexicographically smaller than string $t$ of the same length if there exists an integer $1 \leq i \leq n$ such that $s_j = t_j$ for all $1 \leq j \lt i$, and $s_i \lt t_i$ in alphabetical order. The following illustration shows some examples on some grids and their the lexicographically smallest possible word of length $3$ that you can find within the grids.

你正在玩一个单词谜题。该谜题从一个 $3 \times 3$ 的网格开始，其中每个格子包含字母 A、B 或 C 中的一个。

本谜题的目标是找出长度为 $3$ 的字典序最小的可能单词。该单词可通过选择三个互不相同的格子构成：第一个字母所在的格子与第二个字母所在的格子相邻，第二个字母所在的格子与第三个字母所在的格子相邻。

若两个格子共享一条边或一个角，则称它们彼此相邻，如下图所示。形式化地，若 $(r, c)$ 表示第 $r$ 行、第 $c$ 列的格子，则格子 $(r, c)$ 与以下八个格子相邻：$(r, c + 1)$、$(r - 1, c + 1)$、$(r - 1, c)$、$(r - 1, c - 1)$、$(r, c - 1)$、$(r + 1, c - 1)$、$(r + 1, c)$ 和 $(r + 1, c + 1)$。

请确定在该网格中所能找到的字典序最小的长度为 $3$ 的单词。

长度为 $n$ 的字符串 $s$ 在字典序上小于同样长度的字符串 $t$，当且仅当存在某个整数 $1 \leq i \leq n$，使得对所有 $1 \leq j < i$ 均有 $s_j = t_j$，且 $s_i < t_i$（按字母顺序比较）。下图展示了一些网格示例及其所能找到的字典序最小的长度为 $3$ 的单词。

Input consists of three lines, each containing three letters, representing the puzzle grid. Each letter in the grid can only be either A, B, or C.

输入包含三行，每行包含三个字母，表示谜题的网格。网格中的每个字母只能是 A、B 或 C。

Output the lexicographically smallest possible word of length $3$ that you can find within the grid.

输出你在网格中能找到的字典序最小的长度为 $3$ 的单词。