Count the Number of Good Subsequences

Try to solve the Count the Number of Good Subsequences problem.

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Statement

Count and return the number of good subsequences in the given string s. You may return the modulo 109+710^9 + 7 of the count.

  • A subsequence is a sequence formed from another sequence by deleting some or no elements while keeping the order of the remaining elements unchanged.

  • A good subsequence is a subsequence of a string if it is not empty and the frequency of each character is the same.

Constraints:

  • 1≤1 \leqs.length ≤104\leq 10^4

  • s will only contain lowercase English characters.

Examples

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