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 (3.4.3) (judge verdict: Wrong Answer)

import collections
n = int(input())
dat_a = list(map(int, input().split()))
c = collections.Counter(dat_a)
cc = c.most_common(2)
c1_1 = c1_2 = c2_1 = c2_2 = 0
if len(cc) == 1:
    print(n//2)
else:
    for i in range(n):
        if i % 2 == 0:
            if dat_a[i] == cc[0][0]:
                c1_1 += 1
        else:
            if dat_a[i] == cc[1][0]:
                c1_2 += 1

    for i in range(n):
        if i % 2 == 1:
            if dat_a[i] == cc[0][0]:
                c2_1 += 1
        else:
            if dat_a[i] == cc[1][0]:
                c2_2 += 1

    import math
    if (c1_1 + c1_2) >= (c2_1 + c2_2):
        print( math.ceil(n/2) - c1_1 + math.ceil(n//2) - c1_2)
    else:
        print( math.ceil(n/2) - c2_1 + math.ceil(n//2) - c2_2)