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)

# coding: UTF-8
import sys
#sys.setrecursionlimit(n)
import heapq
import re
import bisect
import random
import math
import itertools
from collections import defaultdict, deque
from copy import deepcopy
from decimal import *

n = int(input())
v = list(map(int, input().split()))
a = defaultdict(int)
b = defaultdict(int)

nn = n // 2
for i in range(nn):
    a[v[i * 2]] += 1
    b[v[i * 2 + 1]] += 1

c = max(a, key=a.get)
d = max(b, key=b.get)
tmpc = a[c]
tmpd = b[d]
a[c] = 0
b[d] = 0

if c == d and tmpc == tmpd:
    print(tmpc)
else:
    if c == d:
        if tmpc > tmpd:
            d2 = max(b, key=b.get)
            b[d] = tmpd
            b[d2] = 0
        else:
            c2 = max(a, key=a.get)
            a[c] = tmpc
            a[c2] = 0
    print(sum(a.values()) + sum(b.values()))