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,sys
n=int(input())
v=list(map(int,input().split()))
a=[]
b=[]
for i in range(0,n,2):
  a.append(v[i-1])
  b.append(v[i])
c=collections.Counter(a)
d=collections.Counter(b)
C=sorted(c.items(), key=lambda x:-x[1])
D=sorted(d.items(), key=lambda x:-x[1])
A=int(C[0][0])
B=int(D[0][0])
cnt=0
if len(set(a))==len(set(b))==1:
  print(n//2)
  sys.exit()
if A!=B:
  for i in range(n//2):
    if a[i]!=A:
      cnt+=1
  for j in range(n//2):
    if b[j]!=B:
      cnt+=1
  print(cnt)
  sys.exit()
if A==B:
  totla=0
  A_=int(C[1][0]) if len(set(a))!=1 else A
  for i in range(n//2):
    if a[i]!=A_:
      totla+=1
  for j in range(n//2):
    if b[j]!=B:
      totla+=1
  totlb=0
  B_=int(D[1][0]) if len(set(b))!=1 else B
  for i in range(n//2):
    if a[i]!=A:
      totlb+=1
  for j in range(n//2):
    if b[j]!=B_:
      totlb+=1
  print(min(totla,totlb))
  sys.exit()