Given an even number ( greater than 2 ), return two prime numbers whose sum will be equal to given number.
NOTE A solution will always exist. read Goldbach’s conjecture
Input : 4 Output: 2 + 2 = 4
If there are more than one solutions possible, return the lexicographically smaller solution.
If [a, b] is one solution with a <= b, and [c,d] is another solution with c <= d, then [a, b] < [c, d] If a < c OR a==c AND b < d.