In mathematics, the factorial of integer n is written as n!. It is equal to the product of n and every integer preceding it. For example: 5! = 1 x 2 x 3 x 4 x 5 = 120
Your mission is simple: Write a function f in class C that takes an integer n and returns the value of n! as a string in full. For zero and all negative numbers, assume result of "1".
Your code must be at or under the par of 140 characters, whitespace included (compact your code into one line!). (Author's best: 125)