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 math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf=10**20
mod=10**9+7

def LI(): return list(map(int,input().split()))
def I(): return int(input())
def LS(): return input().split()
def S(): return input()

def main():
  n=I()
  l=LI()

  l1=[]
  l2=[]

  f=True
  for x in l:
    if f:
      f=False
      l1.append(x)
    else:
      f=True
      l2.append(x)

  l1.sort()
  l2.sort()

  l3=[]
  l4=[]

  a=l1[0]
  c=1
  for x in l1[1:]:
    if a==x:
      c+=1
    else:
      l3.append([a,c])
      a=x
      c=1
  l3.append([a,c])

  a=l2[0]
  c=1
  for x in l2[1:]:
    if a==x:
      c+=1
    else:
      l4.append([a,c])
      a=x
      c=1
  l4.append([a,c])

  l3=sorted(l3,key=lambda x:x[1],reverse=True)
  l4=sorted(l4,key=lambda x:x[1],reverse=True)

  if l3[0][0]==l4[0][0]:
    if l3[0][1]>l4[0][1]:
      return n-l3[0][1]-l4[1][1]
    else:
      if len(l3)==1:
        return n//2
      return n-l3[1][1]-l4[0][1]
  else:
    return n-l3[0][1]-l4[0][1]

print(main())