AtCoder Grand Contest 072
D
Magician
AtCoder
⌀ 4043
原题
← CE →
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Problem Statement

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This is an interactive problem.

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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.

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Example For $N = 2$, the fronts of cards $1$, $2$, $3$, $4$, $5$, $6$ are 0011, 0101, 0110, 1001, 1010, 1100, respectively.

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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.

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A single magic

  1. The host announces a letter $s$ among the first $N$ uppercase letters.
  2. The host writes a length-$2N$ string of all 0 on the blackboard.
  3. 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 to 1.
  1. 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 $s$.
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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.

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Implement a strategy that makes all $T$ magics succeed. Now, let us begin.

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Constraints

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  • $2 \le N \le 10$
  • $1 \le T \le 5\,000$
  • 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.
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Input and Output

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First, read the integers $N$ and $T$ given from Standard Input in the following format:

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N T

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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.

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c_1 c_2 \cdots c_{\tbinom{2N}{N}}

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Next, repeat the following process $T$ times. The $t$-th iteration $(1 \leq t \leq T)$ corresponds to the $t$-th magic.

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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 -1 is 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.)

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Note

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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.

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Sample Interaction

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Note that this is just an example of interaction.

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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.
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题目信息
题号
agc072_d
时间限制
4 s
内存限制
1024 MB

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