We all know and love our Fibonacci sequence and have seen a myriad of challenge on it here already. However, we're still lacking a very simple case which this answer is going to provide: Reversed fibonacci! So given
F_n your job is to find
Your input will be a non-negative integer, which is guaranteed to be part of the fibonacci sequence.
The output must be a non-negative integer as well.
What to do?
The introduction already said: Given a fibonacci number, output its index. Fiboancci number hereby is defined as
F(0)=0, F(1)=1, F(n)=F(n-1)+F(n-2) and you're given
F(n) and must return
Potential Corner Cases
0 is a valid in- and output.
If given "1" as input you may either output "1" or "2", as you prefer.
You may always assume that your input actually is a fibonacci number.
You may assume that the input is representable as a 32-bit signed integer.
This is code-golf so the shortest answer in bytes wins!
Standard rules apply of course.
0 -> 0 2 -> 3 3 -> 4 5 -> 5 8 -> 6 13 -> 7 1836311903 -> 46