Kata

You are given some positive integer num (10^11 > num > 0).

Task is simple:

• try to find out the biggest divisor of this number (not including value itself) and return it;
• if it's a prime number, return 1.

Hint: you'll have some problems (12 seconds time exceeded) if not find best time complexity (must be significantly less then O(num)).

Examples:

if num equals 12, its biggest divisor will be 6 
(we shoul choose maximum between 1, 2, 3, 4, 6, 12, 
but not including the number itself, i.e. 12)

if num equals 7, its biggest divisor will be 1, 
because it's a prime number 
(we shoul choose maximum between 1, 7, 
but not including the number itself, i.e. 7)