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)

# -*- coding: utf-8 -*-
import collections

N = int(input())
V = list(map(int, input().split()))

odd = V[::2]
even = V[1:N:2]

odd_d = collections.Counter(odd)
even_d = collections.Counter(even)

if odd == even and len(odd_d) == 1 and len(even_d) == 1:
    ans = len(odd)

elif len(odd_d) == 1 and len(even_d) == 1:
    ans = 0

else:
    for i,n in enumerate(odd_d.keys()):
        if i == 0:
            odd_ind = n
        elif i == 1:
            odd_ind2 = n
        else:
            break
    for i, n in enumerate(even_d.keys()):
        if i == 0:
            even_ind = n
        elif i == 1:
            even_ind2 = n
        else:
            break

    if odd_ind != even_ind:
        ans = (N//2 - odd_d[odd_ind]) + (N//2 - even_d[even_ind])
    else:
        if odd_d[odd_ind] >= even_d[even_ind]:
            ans = (N//2 - odd_d[odd_ind]) + (N//2 - even_d[even_ind2])
        else:
            ans = (N//2 - odd_d[odd_ind2]) + (N//2 - even_d[even_ind])
print(ans)