#5503. CSES2421 计数重排
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CSES2421 计数重排
Counting Reorders
Calculate the number of ways you can reorder the characters of a string so that no two adjacent characters are the same. For example, the answer for aabc is 6, because the possible orders are abac, abca, acab, acba, baca, and caba.
Input
The only input line has a string that consists of n characters between a–z.
Output
Print an integer: the answer modulo 10^9+7.
Constraints
Example
Input
aabc
Output
6