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 PyPy3 (2.4.0) (judge verdict: Accepted)

import collections
n = int(input())
v = list(map(int, input().split()))

odd = []
even = []

for i in range(n):
  if i % 2 == 0:
    odd.append(v[i])
  else:
    even.append(v[i])

oddm = collections.Counter(odd)
evenm = collections.Counter(even)

odd1 = oddm.most_common()[0]
even1 = evenm.most_common()[0]

if (odd1 == even1) and (oddm.most_common()[0][1] + evenm.most_common()[0][1] == n):
  ans = n//2
else:
  if odd1 != even1:
    ans = n - oddm.most_common()[0][1] - evenm.most_common()[0][1] 
  else:
    p1 = ans = n - oddm.most_common()[1][1] - evenm.most_common()[0][1] 
    p2 = ans = n - oddm.most_common()[0][1] - evenm.most_common()[1][1] 
    ans = min(p1, p2)
    
print(ans)