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)

from itertools import *
from collections import Counter

N = int(input())
v = list(map(int,input().split()))
d = Counter(v).most_common()
most_common = d[0][0]
try:
    second_common = d[1][0]
except:
    print(N//2)
    exit()
try:
    third_common = d[2][0]
except:
    third_common = float('Inf')

def f(v,m,s):
    cnt = 0
    for j in range(N):
        if j % 2 != 0:
            if v[j] != m:
                cnt += 1
        else:
            if v[j] != s:
                cnt += 1
    return cnt

p = [most_common,second_common,third_common]
p = list(product(p,p))
p = [i for i in p if i[0] != i[1]]
ans = float('inf')
for i in p:
    tmp = f(v,i[0],i[1])
    ans = min(ans,tmp)
print(ans)