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No.3318 Pouring Egg on Customers

レベル : / 実行時間制限 : 1ケース 2.000秒 / メモリ制限 : 512 MB / 小数誤差許容問題 相対誤差が $10^{-8}$ 以下。ただし、ジャッジ側の都合で500桁未満にしてください
タグ : (解説公開後に AC するまで非表示) / 解いたユーザー数 10
作問者 : Andrew8128 / テスター : ゆにたりー卿 DeltaStruct kazuppa elphe のらら Rice_tawara459 👑 みうね 👑 seekworser
お気に入りにしたユーザー ProblemId : 12566 / 自分の提出
問題文最終更新日: 2025-10-30 02:00:28
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第2回 岩井星人アンソロジープログラミングコンテスト Div.1 (順位表) の他の問題:

Problem Statement

Iwai Seijin plans to work part-time at an okonomiyaki restaurant for at most $N$ days starting now. Initially, his skill at cooking okonomiyaki is $X$, and he has $0$ yen.
Each day, he chooses one of the following two actions.

  • Attend training: His skill increases by $Y$, and he earns $P$ yen as the daily wage for the training period.
  • Perform regular duties: He earns $Q$ yen as the daily wage. However, with probability $ \frac{1}{\text{skill}} $, he pours egg on a customer. If he pours egg on a customer, he chooses one of the following.
    • Pay $R$ yen to serve the customer a complimentary lemon sour and cover up the incident (his money may become negative in this case).
    • Do not cover it up; the manager finds out, and he is fired that same day.
    Note that even if he is fired, he still receives that day's wage of $Q$ yen.

The job ends when $N$ days have passed or when he is fired.
Iwai Seijin chooses his actions so as to maximize the expected value of his money at the time the job ends. Find the expected value of his money when the job ends.

You are given $T$ test cases. Find the answer for each of them.

Constraints

    All input values are integers
    $1 \leq T \leq 300$
    $1 \leq N \leq 10^{12}$
    $1 \leq X, Y \leq 100$
    $1 \leq P \leq Q \leq 10^5$
    $1 \leq R \leq 10^5$

Input

The input is given from standard input in the following format, where $\mathrm{case}_i$ denotes the $i$-th test case.

$T$
$\mathrm{case}_1$
$\mathrm{case}_2$
$\vdots$
$\mathrm{case}_T$

Each test case is given in the following format.

$N$
$X\ Y$
$P\ Q\ R$

Output

Output $T$ lines.
On the $i$-th line, output the expected value of his money at the end of the job for the $i$-th test case.
Your answer is judged correct if the relative error is at most $10^{-8}$.

Sample

Sample
Input
5
1
1 1
1 2 10000
2
3 1
1 2 10000
2
3 1
1 2 1
3000
1 1
800 1000 200
1000000000000
100 100
100000 100000 100000
Output
2.0000000000
3.3333333333
3.6666666667
2978490.9090909091
100000000000000000.0000000000

In the 1st test case, Iwai Seijin's skill is $1$, so performing regular duties makes him pour egg on a customer with 100% probability; nevertheless, it is optimal to perform regular duties, pour egg on the customer, and get fired.

In the 2nd test case, it is optimal to perform regular duties on both day 1 and day 2.
With probability $ \frac{2}{3} $, he does not pour egg on a customer on day 1, and in this case Iwai Seijin's final money is $4$ yen.
With probability $ \frac{1}{3} $, he pours egg on a customer on day 1; in this case it is optimal for Iwai Seijin to get fired without covering it up, and his final money is $2$ yen.
Therefore, the answer is $ \frac{2}{3} \times 4 + \frac{1}{3} \times 2 = \frac{10}{3} $.

In the 3rd test case, it is optimal to perform regular duties on both day 1 and day 2.
With probability $ \frac{2}{3} $, he does not pour egg on a customer on day 1, and in this case Iwai Seijin's final money is $4$ yen.
With probability $ \frac{1}{3} $, he pours egg on a customer on day 1; in this case it is optimal for Iwai Seijin to pay $1$ yen and cover it up, and his final money is $3$ yen.
Therefore, the answer is $ \frac{2}{3} \times 4 + \frac{1}{3} \times 3 = \frac{11}{3} $.

Note that, as this test case illustrates, the sum of $N$ over the test cases is not necessarily at most $10^{12}$.

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