题目描述
There is a set $S$ of $n$ points on a coordinate plane.
Kanno starts from a point $P$ that can be chosen on the plane. $P$ is not added to $S$ if it doesn't belong to $S$. Then the following sequence of operations (altogether called a move) is repeated several times, in the given order:
- Choose a line $l$ such that it passes through at least two elements in $S$ and passes through Kanno's current position. If there are multiple such lines, one is chosen equiprobably.
- Move to one of the points that belong to $S$ and lie on $l$. The destination is chosen equiprobably among all possible ones, including Kanno's current position (if it does belong to $S$).
There are $q$ queries each consisting of two integers $(t_i, m_i)$. For each query, you're to help Kanno maximize the probability of the stopping position being the $t_i$-th element in $S$ after $m_i$ moves with a proper selection of $P$, and output this maximum probability. Note that according to rule 1, $P$ should belong to at least one line that passes through at least two points from $S$.
Input
The first line contains a positive integer $n$ ($2 \leq n \leq 200$) — the number of points in $S$.
The $i$-th of the following $n$ lines contains two space-separated integers $x_i$ and $y_i$ ($-10^4 \leq x_i, y_i \leq 10^4$) — the coordinates of the $i$-th point in $S$. The input guarantees that for all $1 \leq i \lt j \leq n$, $(x_i, y_i) \neq (x_j, y_j)$ holds.
The next line contains a positive integer $q$ ($1 \leq q \leq 200$) — the number of queries.
Each of the following $q$ lines contains two space-separated integers $t$ and $m$ ($1 \leq t_i \leq n$, $1 \leq m_i \leq 10^4$) — the index of the target point and the number of moves, respectively.
Output
Output $q$ lines each containing a decimal number — the $i$-th among them denotes the maximum probability of staying on the $t_i$-th point after $m_i$ steps, with a proper choice of starting position $P$.
Your answer will be considered correct if each number in your output differs from the corresponding one in jury's answer by at most $10^{-6}$.
Formally, let your answer be $a$, and the jury's answer be $b$. Your answer is considered correct if $|a - b| \le 10^{-6}$.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
样例输出
提示
The points in $S$ and possible candidates for line $l$ are depicted in the following figure.
For the first query, when $P = (-1, -3)$, $l$ is uniquely determined to be $3x = y$, and thus Kanno will move to $(0, 0)$ with a probability of $\frac 1 2$.
For the third query, when $P = (2, 2)$, $l$ is chosen equiprobably between $x + y = 4$ and $x = y$. Kanno will then move to the other four points with a probability of $\frac 1 2 \cdot \frac 1 3 = \frac 1 6$ each, or stay at $(2, 2)$ with a probability of $\frac 1 3$.