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
def solve():
  n = int(input())
  odd = []
  even = []
  a = list(int(i) for i in input().split())
  for i in range(n):
    if i%2 == 0:
      odd.append(a[i])
    else:
      even.append(a[i])
  ans = 0
  c1 = collections.Counter(odd)
  c2 = collections.Counter(even)
  n1 = len(odd)
  n2 = len(even)
  if c1 == c2:
    print(min(n-n2,n-n1))
    exit()
  
  if c1.most_common()[0][0]  ==   c2.most_common()[0][0]:
         ans += min((n1-c1.most_common()[1][1]),(n2-c2.most_common()[1][1]))
         ans += min(n2-c2.most_common()[0][1],n1-c1.most_common()[0][1])
  else:
         ans +=n1-c1.most_common()[0][1]+n2-c2.most_common()[0][1]
  print(ans)
                  
                  
solve()