X marks the Spot

Hyby, who loves puzzles, decided to set another puzzle problem this year, as he did last year.

This time the topic is Indirect Indexing, and the rules are as follows.

1. You are given $N$ pairs of strings $(S_1,T_1), (S_2,T_2), \ldots, (S_N,T_N)$. For each pair, the length of $S_i$ equals the length of $T_i$.
2. Let $P_i$ be the position where the letter x or X appears in $S_i$. This position is always unique.
3. Read the $P_i$-th letter of $T_i$. However, lowercase letters must be converted to uppercase.
4. For example, if $S_i$ is Indexing and $T_i$ is Indirect, the letter read is R.

The first line contains the number of string pairs $N$. ($1 \le N \le 500\,000$)

From the second line onward, line $i+1$ contains the pair of strings $S_i$ and $T_i$, separated by a space. The total length of all input strings does not exceed $1\,000\,000$, and every string consists only of English letters (uppercase or lowercase) and digits.

Print the letters read for the $N$ string pairs, in order, concatenated on a single line.