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Beautiful Mirrors

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Description:

Creatnx has $$$n$$$ mirrors, numbered from $$$1$$$ to $$$n$$$. Every day, Creatnx asks exactly one mirror "Am I beautiful?". The $$$i$$$-th mirror will tell Creatnx that he is beautiful with probability $$$\frac{p_i}{100}$$$ for all $$$1 \le i \le n$$$.

Creatnx asks the mirrors one by one, starting from the $$$1$$$-st mirror. Every day, if he asks $$$i$$$-th mirror, there are two possibilities:

  • The $$$i$$$-th mirror tells Creatnx that he is beautiful. In this case, if $$$i = n$$$ Creatnx will stop and become happy, otherwise he will continue asking the $$$i+1$$$-th mirror next day;
  • In the other case, Creatnx will feel upset. The next day, Creatnx will start asking from the $$$1$$$-st mirror again.

You need to calculate the expected number of days until Creatnx becomes happy.

This number should be found by modulo $$$998244353$$$. Formally, let $$$M = 998244353$$$. It can be shown that the answer can be expressed as an irreducible fraction $$$\frac{p}{q}$$$, where $$$p$$$ and $$$q$$$ are integers and $$$q \not \equiv 0 \pmod{M}$$$. Output the integer equal to $$$p \cdot q^{-1} \bmod M$$$. In other words, output such an integer $$$x$$$ that $$$0 \le x < M$$$ and $$$x \cdot q \equiv p \pmod{M}$$$.

Input:

The first line contains one integer $$$n$$$ ($$$1\le n\le 2\cdot 10^5$$$) — the number of mirrors.

The second line contains $$$n$$$ integers $$$p_1, p_2, \ldots, p_n$$$ ($$$1 \leq p_i \leq 100$$$).

Output:

Print the answer modulo $$$998244353$$$ in a single line.

Sample Input:

1
50

Sample Output:

2

Sample Input:

3
10 20 50

Sample Output:

112

Note:

In the first test, there is only one mirror and it tells, that Creatnx is beautiful with probability $$$\frac{1}{2}$$$. So, the expected number of days until Creatnx becomes happy is $$$2$$$.

Informação

Codeforces

Provedor Codeforces

Código CF1265E

Tags

data structuresdpmathprobabilities

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Datas 09/05/2023 09:54:41

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