Problem:
Score : 300 points

Problem Statement

A sequence a_1,a_2,... ,a_n is said to be /\/\/\/ when the following conditions are satisfied:

For each i = 1,2,..., n-2, a_i = a_{i+2}.

Exactly two different numbers appear in the sequence.

You are given a sequence v_1,v_2,...,v_n whose length is even.
We would like to make this sequence /\/\/\/ by replacing some of its elements.
Find the minimum number of elements that needs to be replaced.

Constraints

2 \leq n \leq 10^5

n is even.

1 \leq v_i \leq 10^5

v_i is an integer.

Input

Input is given from Standard Input in the following format:

n
v_1 v_2 ... v_n

Output

Print the minimum number of elements that needs to be replaced.

Sample Input 1

4
3 1 3 2

Sample Output 1

1

The sequence 3,1,3,2 is not /\/\/\/, but we can make it /\/\/\/ by replacing one of its elements: for example, replace the fourth element to make it 3,1,3,1.

Sample Input 2

6
105 119 105 119 105 119

Sample Output 2

0

The sequence 105,119,105,119,105,119 is /\/\/\/.

Sample Input 3

4
1 1 1 1

Sample Output 3

2

The elements of the sequence 1,1,1,1 are all the same, so it is not /\/\/\/.

Solution in Python (2.7.6) (judge verdict: Wrong Answer)

import collections

def main():
    n = input()
    a = map(int, raw_input().split())
    odd = [a[2 * i] for i in range(n/2)]
    even = [a[2*i + 1] for i in range(n/2)]
    codd = collections.Counter(odd)
    ceven = collections.Counter(even)
    coddmostitem = codd.most_common()[0][0]
    coddmosttimes = codd.most_common()[0][1]
    cevenmostitem = ceven.most_common()[0][0]
    cevenmosttimes = codd.most_common()[0][1]
    if coddmostitem == cevenmostitem:
        if coddmosttimes >= cevenmosttimes:
            if len(ceven) == 1:
                cevennoreplace = 0
            else:
                cevennoreplace = ceven.most_common()[1][1]
            coddnoreplace = codd.most_common()[0][1]
        if coddmosttimes < cevenmosttimes:
            if len(codd) == 1:
                coddnoreplace = 0
            else:
                coddnoreplace = codd.most_common()[1][1]
            cevennoreplace = ceven.most_common()[0][1]
    else:
        coddnoreplace = codd.most_common()[0][1]
        cevennoreplace = ceven.most_common()[0][1]
    coddreplace = n/2 - coddnoreplace
    cevenreplace = n/2 - cevennoreplace
    print(coddreplace+cevenreplace)

if __name__ == '__main__':
    main()