https://en.wikipedia.org/wiki/Natural_logarithm
- https://ideone.com/KcGlMR (C language )
- https://ideone.com/qAzN74 ( Kotlin language )
- https://repl.it/@emilstates/nat-log ( Kotlin language )\
- https://ideone.com/N6q3WE (in Ruby Language)
- https://ideone.com/thinkphp/nat-log