You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "how many digits is a social security number?" whose answer is nine.
Each document should contain about 30 words, and these documents should contain useful information.

Query: how many digits is a social security number
Useful Output:

Doc 1: How Many Digits Are Social Security Numbers? Unlock the secrets behind one of the most important identifiers in the United States: the
Doc 2: Your unique 9-digit Social Security number follows you throughout your lifetime. How did this number's importance evolve?
Doc 3: The nine-digit combination of numbers, taking into account the combinations not allowed, gives the agency around 900 million unique Social
Doc 4: Every Social Security number consists of nine digits, typically formatted as XXX-XX-XXXX. This familiar pattern divides the number into three
Doc 5: Since June 2011, Social Security numbers (SSNs) have been assigned randomly, but they still have the nine-digit, XXX-XX-XXXX format used