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
from operator import itemgetter

N = int(input())

up = []
down = []
for i, v in enumerate(list(map(int, input().split()))):
    if i % 2 == 0:
        up.append(v)
    else:
        down.append(v)

ud = collections.Counter(up)
dd = collections.Counter(down)

ul = []
for u, c in ud.items():
    ul.append([u, c])
dl = []
for d, c in dd.items():
    dl.append([d, c])

ul.sort(key=itemgetter(1))
dl.sort(key=itemgetter(1))

if ul[0][0] != dl[0][0]:
    print(N - ul[0][1] - dl[0][1])
elif len(ul) == 1 and len(dl) > 1:
    print(N - ul[0][1] - dl[1][1])
elif len(ul) > 1 and len(dl) == 1:
    print(N - ul[1][1] - dl[0][1])
elif len(ul) == 1 and len(dl) == 1:
    print(N//2)
else:
    print(N - max(ul[0][1]+dl[1][1], ul[1][1]+dl[0][1]))