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: Runtime Error)

#!/usr/bin/env python3
import sys
import statistics
import collections

def solve(n: int, v: "List[int]"):
    half_length = len(v) // 2
    O = [v[i] for i in range(1, n, 2)]
    E = [v[i] for i in range(0, n, 2)]

    co = list(collections.Counter(O).most_common())
    ce = list(collections.Counter(E).most_common())
    o1 = co[0][0]
    e1 = ce[0][0]

    O_ = list(filter(lambda o: o != o1, O))
    E_ = list(filter(lambda e: e != e1, E))
    num_o_1 = len(O_) 
    num_e_1 = len(E_)

    if e1 != o1:
        num = num_o_1 + num_e_1
    else:
        if (len(co) == 1) and (len(ce) == 1):
            num = half_length
        elif len(co) == 1:
            e2 = ce[1][0]
            num_e_2 = len(list(filter(lambda e: e != e2, E)))
            num = num_o_1 + num_e_2
        elif len(ce) == 1:
            o2 = co[1][0]
            num_o_2 = len(list(filter(lambda o: o != o2, O)))
            num = num_o_2 + num_e_1
        else:
            e2 = ce[1][0]
            o2 = co[1][0]
            num = min(num_o_1 + num_e_2, num_o_2 + num_e_1)
    print(num)
    return


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    n = int(next(tokens))  # type: int
    v = [ int(next(tokens)) for _ in range(n) ]  # type: "List[int]"
    solve(n, v)

if __name__ == '__main__':
    main()