Mercurialist
Time limit2sMemory limit1024 MB
Alice drinks from X elixir, Y mercury, and Z yogurt bottles in random order; find her survival probability as a fraction modulo 998244353.
- Level
Medium7 of 10
- Topics
- Probability, Combinatorics, Math
- Solved
- No attempts yet
Problem
This country has a medicine for immortality. Alice got bottles from the Hatter.
bottles contain elixir. If Alice drinks it, she will immediately become immortal.
bottles contain mercury, and each has a different toxicity. If she drinks the -th bottle, the following event will occur after days.
- Event : Alice will immediately die if she has not drunk the elixir before event . If she has drunk the elixir, she won't die.
The remaining bottles contain yogurt. Nothing will happen when Alice drinks it.
At the same time every morning, Alice chooses one non-empty bottle with equal probability and drinks it. If all bottles are empty, she does nothing.
Answer the probability that Alice will be alive days after the first day she starts drinking bottles. Alice won't die other than events.
The probability can be expressed as using coprime integers and . Output a non-negative integer less than such that . The probability is a rational number, and is uniquely determined under the conditions of this problem.
Input
Output
Output defined in the statement. Add a new line at the end of the output.
Constraints
All inputs are integers.
Hint
In Sample Input 1, Alice dies only if she drinks mercury on day 1 and yogurt on day 2. The probability of death is , so the answer is .
In Sample Input 2, Alice never dies.