Problem Statement
This is an interactive problem.
There are $\tbinom{2N}{N}$ cards numbered $1$ to $\tbinom{2N}{N}$ on a desk. Card $i$ $(1 \le i \le \tbinom{2N}{N})$ shows on its front the $i$‑th string in lexicographic order among the strings consisting of $N$ zeros and $N$ ones.
Example For $N = 2$, the fronts of cards $1$, $2$, $3$, $4$, $5$, $6$ are 0011, 0101, 0110, 1001, 1010, 1100, respectively.
Witch Alice writes one of the first $N$ uppercase letters (for example, A or B if $N = 2$) on the back of each card, then performs the following magic $T$ times.
A single magic
- The host announces a letter
$s$among the first$N$uppercase letters.- The host writes a length-
$2N$string of all0on the blackboard.- For
$i = 1, 2, \dots, N$in this order, do the following. Here,$a_1, b_1, \dots, a_N, b_N$are distinct integers from$1$to$2N$.
- First, the host tells Alice integers
$a_i$and$b_i$.
- Then, Alice chooses exactly one of the
$a_i$-th and$b_i$-th characters of the string on the blackboard, and sets it to1.
- Let
$x$be the final string on the blackboard. Exactly one card shows$x$on its front; look at its back. The magic succeeds if and only if the letter on its back equals$s$.
Note that Alice learns $a_{i+1}$ and $b_{i+1}$ only after choosing which of the $a_i$-th and $b_i$-th characters to set to 1.
Implement a strategy that makes all $T$ magics succeed. Now, let us begin.
Constraints
$2 \le N \le 10$$1 \le T \le 5\,000$- The letter
$s$is among the first$N$uppercase letters. $1 \le a_i < b_i \le 2N$$a_1, b_1, a_2, b_2, \dots, a_N, b_N$are distinct.$a_1, b_1, a_2, b_2, \dots, a_N, b_N, s$are fixed before the interaction starts.$N, T, a_i, b_i$are integers.
Input and Output
First, read the integers $N$ and $T$ given from Standard Input in the following format:
N T
Next, let $c_i$ be the letter written on the back of card $i$, and print those letters in the following format, followed by a newline. Here, $c_i$ must be among the first $N$ uppercase letters.
c_1 c_2 \cdots c_{\tbinom{2N}{N}}
Next, repeat the following process $T$ times. The $t$-th iteration $(1 \leq t \leq T)$ corresponds to the $t$-th magic.
Read the announced letter
$s$given in the following format:> s >Then, for
$i = 1, 2, \dots, N$in this order, do the following.
- Read integers
$a_i$and$b_i$given in the following format:> a_i b_i >
- Print the chosen position
$d$in the following format, followed by a newline. Here,$d$must be$a_i$or$b_i$.> d >If your output was malformed or the previous magic failed, no more input such as
$s$or$(a_i, b_i)$is given, but-1is given from Standard Input. In this case, exit immediately. (If you fail for the first time in the$T$-th magic, or your output was malformed for the first time at$i = N$in the$T$-th magic, no more input follows.)
Note
Flush after every output. Otherwise, you may receive a TLE verdict. If you read -1, exit immediately. If you do so, you will receive a WA verdict, but continuing leads to an indeterminate verdict. Unnecessary newlines may be seen as malformed. The judge is non‑adaptive; the values $a_1, b_1, a_2, b_2, \dots, a_N, b_N, s$ are fixed before the interaction starts, and will not be affected by your output.
Sample Interaction
Note that this is just an example of interaction.
| Input | Output | Comment |
|---|---|---|
2 2 |
The integers $N$ and $T$ are given from Standard Input. |
|
ABABAB |
Print letters for the backs of the six cards. | |
A |
The first magic begins. The host declares A. |
|
1 2 |
The host tells you $(a_1, b_1) = (1, 2)$. |
|
2 |
Set the second character to 1. |
|
3 4 |
The host tells you $(a_2, b_2) = (3, 4)$. |
|
3 |
Set the third character to 1. The final string is 0110, and the card with 0110 on its front has A on the back, so the magic succeeds. |
|
B |
The second magic begins. The host declars B. |
|
1 3 |
The host tells you $(a_1, b_1) = (1, 3)$. |
|
1 |
Set the first character to 1. |
|
2 4 |
The host tells you $(a_2, b_2) = (2, 4)$. |
|
2 |
Set the second character to 1. The final string is 1100, and the card with 1100 on its front has B on the back, so the magic succeeds. |
题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。