How to declare array size based on another value (C) [duplicate]
Solution 1:
What you're asking for is a variable length array, and such arrays are not supported in MSVC, although they are supported in gcc.
If you're stuck with MSVC, your only option is to dynamically allocate the memory.
int *ln = malloc((fb-1) * sizeof *ln);
Be sure to call free on this memory after you're done using it.