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 operator import itemgetter
N = int(input())
A = list(map(int, input().split()))

O = {}
E = {}

for i in range(N//2):
  if A[2*i] in O:
    O[A[2*i]] += 1
  else:
    O[A[2*i]] = 1
  if A[2*i+1] in E:
    E[A[2*i+1]] += 1
  else:
    E[A[2*i+1]] = 1

O = sorted(O.items(), key=itemgetter(1), reverse=True)      
E = sorted(E.items(), key=itemgetter(1), reverse=True)   

if O[0][0] != E[0][0]:
  print(N - O[0][1] - E[0][1])
else:
  if O[0][1] >= E[0][1]:
    print(N - O[0][1] - (E[1][1] if len(E) > 1 else 0))
  else:
    print(N - E[0][1] - (O[1][1] if len(O) > 1 else 0))