310968: CF1915B. Not Quite Latin Square

A Latin square is a $3 \times 3$ grid made up of the letters $\texttt{A}$, $\texttt{B}$, and $\texttt{C}$ such that:

• in each row, the letters $\texttt{A}$, $\texttt{B}$, and $\texttt{C}$ each appear once, and
• in each column, the letters $\texttt{A}$, $\texttt{B}$, and $\texttt{C}$ each appear once.

You are given a Latin square, but one of the letters was replaced with a question mark $\texttt{?}$. Find the letter that was replaced.

The first line of the input contains a single integer $t$ ($1 \leq t \leq 108$) — the number of testcases.

Each test case contains three lines, each consisting of three characters, representing the Latin square. Each character is one of $\texttt{A}$, $\texttt{B}$, $\texttt{C}$, or $\texttt{?}$.

Each test case is a Latin square with exactly one of the letters replaced with a question mark $\texttt{?}$.

For each test case, output the letter that was replaced.

3
ABC
C?B
BCA
BCA
CA?
ABC
?AB
BCA
ABC

A
B
C

The correct Latin squares for the three test cases are shown below:

$$\begin{bmatrix} \texttt{A} & \texttt{B} & \texttt{C} \\ \texttt{C} & \color{red}{\texttt{A}} & \texttt{B} \\ \texttt{B} & \texttt{C} & \texttt{A} \\ \end{bmatrix} \quad \begin{bmatrix} \texttt{B} & \texttt{C} & \texttt{A} \\ \texttt{C} & \texttt{A} & \color{red}{\texttt{B}} \\ \texttt{A} & \texttt{B} & \texttt{C} \\ \end{bmatrix} \quad \begin{bmatrix} \color{red}{\texttt{C}} & \texttt{A} & \texttt{B} \\ \texttt{B} & \texttt{C} & \texttt{A} \\ \texttt{A} & \texttt{B} & \texttt{C} \\ \end{bmatrix}$$