Finding the minimal period T of array a

You are given an array a of length n = 2m. Write a function that finds length of the minimal period T of array a.

int MinPeriod(int * a, int n)

Number T is a period of array a, if repeating first T elements of array a several times gives exactly array a, without any extra elements.

Examples:
Input   Output
n = 8
a = {2, 5, 3, 4, 2, 5, 3, 4}    4
n = 8
a = {2, 5, 3, 2, 5, 3, 2, 5}    8