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 defaultdict
N = int(input())
V = list(map(int,input().split()))
V1 = []
V2 = []
for i in range(N):
    if i % 2 == 0:
        V1.append(V[i])
    else:
        V2.append(V[i])

dic1 = defaultdict(int)
for v in V1:
    dic1[v] += 1
dic1 = sorted(dic1.items(), key=lambda x:x[1], reverse=True)

dic2 = defaultdict(int)
for v in V2:
    dic2[v] += 1
dic2 = sorted(dic2.items(), key=lambda x:x[1], reverse=True)

if dic1[0][0] != dic2[0][0]:
    ans = (N//2 - dic1[0][1]) + (N//2 - dic2[0][1])
else:
    ans1 = N//2 - dic1[0][1]
    if len(dic2) >= 2:
        ans1 += N//2 - dic2[1][1]
    else:
        ans1 += N//2

    ans2 = N//2 - dic2[0][1]
    if len(dic1) >= 2:
        ans2 += N//2 - dic1[1][1]
    else:
        ans2 += N//2

    ans = min(ans1, ans2)

print(ans)