title: Extremely big integer multiplication and addition
body: <p>Greetings,</p>
  
  <p>I need to multiply two extremely long integer values stored in a text file (exported via GMP (MPIR, to be exact), so they can be any in any base). Now, I would usually just import these integers via the mpz_inp_str() function and perform the multiplication in RAM, however, these values are so long that I can't really load them (about 1 GB of data each). What would be the fastest way to do this? Perhaps there are some external libraries that do this sort of thing already? Are there any easily implementable methods for this (performance is not incredibly important as this operation would only be performed once or twice)?</p>
  
  <p>tl;dr: I need to multiply values so large they don't fit into process memory limits (Windows).</p>
  
  <p>Thank you for your time.</p>