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 C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

int main() {
  int n;
  cin >> n;
  
  vector<int> v0(100000,0), v1(100000,0);
  int l, m;
  for (int i = 0; i < n/2; i++) {
    cin >> l >> m;
    v0.at(l-1)++;
    v1.at(m-1)++;
  }

  int index0_1 = 0, index0_2 = 0, index1_1 = 0, index1_2 = 0;
  for (int i = 0; i < 100000; i++) {
    if (v0.at(i) > v0.at(index0_1)) {
      index0_1 = i;
      index0_2 = index0_1;
    }
    else if (v0.at(i) > v0.at(index0_2)) {
	index0_2 = i;
    }
    if (v1.at(i) > v1.at(index1_1)) {
      index1_1 = i;
      index1_2 = index1_1;
    }
    else if (v1.at(i) > v1.at(index1_2)) {
	index1_2 = i;
    }
  }

  if (index0_1 == index1_1) {
    cout << n - max(v0.at(index0_2) + v1.at(index1_1),v0.at(index0_1) + v1.at(index1_2)) << endl;
  }
  else {    
    cout << n - v0.at(index0_1) - v1.at(index1_1) << endl;
  }
}