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)

from collections import Counter
n = int(input())
V = list(map(int, input().split()))

c1 = Counter(V[::2])
c2 = Counter(V[1::2])
# print('c1, c2', c1, c2)

c1_items = sorted(c1.items(), key=lambda x: -x[1])
c2_items = sorted(c2.items(), key=lambda x: -x[1])
c1_max = c1_items[0][1]
c2_max = c2_items[0][1]
c1_second = 0
c2_second = 0

c1_max_group = set()
for key, value in c1_items:
    if value == c1_max:
        c1_max_group.add(key)
    else:
        c1_second = value
        break
c2_max_group = set()
for key, value in c2_items:
    if value == c2_max:
        c2_max_group.add(key)
    else:
        c2_second = value
        break

# print(c1_max_group, c1_max, c1_second)
# print(c2_max_group, c2_max, c2_second)
if len(c1_max_group) == 1 and len(c2_max_group) == 1 and list(
        c1_max_group)[0] in c2_max_group:
    v1 = n - c1_max - c2_second
    v2 = n - c1_second - c2_max
    ans = min(v1, v2)
else:
    ans = n - c1_max - c2_max
print(ans)