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


def main():
    n = int(input())
    aa = list(map(int, input().split()))
    cs_a0 = Counter(a for i, a in enumerate(aa) if i % 2 == 0)
    cs_a1 = Counter(a for i, a in enumerate(aa) if i % 2 == 1)
    vs_a0 = sorted(((v, k) for k, v in cs_a0.items()), reverse=True)
    vs_a1 = sorted(((v, k) for k, v in cs_a1.items()), reverse=True)
    if vs_a0[0][1] != vs_a1[0][1]:
        print(n - vs_a0[0][0] - vs_a1[0][0])
    else:
        res = 1 << 30
        if len(vs_a0) == 1 and len(vs_a1) == 1:
            res = n // 2
        if len(vs_a0) > 1:
            res = min(res, n - vs_a0[1][0] - vs_a1[0][0])
        if len(vs_a1) > 1:
            res = min(res, n - vs_a0[0][0] - vs_a1[1][0])
        print(res)


if __name__ == "__main__":
    main()