This library is a bignum library written in C language (but use some C++ STL). It use doubly linked list to store each digit of number, hence the name "longnum", which means it can store arbittary length of number. This isn't the most efficeint way to keep number in memory, it's purpose is to extract each digit of number easily. It's firstly written to find the amount of zero following the 1000 factorial as a solution to 2nd POSN camp.