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: Accepted)

import collections

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

l1 = []
l2 = []
for i in range(n):
    if i % 2 == 0:
        l1.append(v[i])
    else:
        l2.append(v[i])

counter1 = collections.Counter(l1)
counter2 = collections.Counter(l2)

mode_v1 = counter1.most_common()
mode_v2 = counter2.most_common()
# print(mode_v1, mode_v2)

if mode_v1[0][0] != mode_v2[0][0]:
    print(n - mode_v1[0][1] - mode_v2[0][1])
else:
    if len(set(v)) == 1:
        print(n // 2)
    elif len(set(l1)) == 1:
        print(mode_v2[0][1])
    elif len(set(l2)) == 1:
        print(mode_v1[0][1])
    else:
        print(min(n - mode_v1[0][1] - mode_v2[1][1], n - mode_v1[1][1] - mode_v2[0][1]))