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: Accepted)

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <utility>
#include <string>
#include <stack>
#include <regex>
#include <cctype>

#define REP(i, n) for (int i = 0; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define vi vector<int>
#define vvi vector<vector<int>>
#define vl vector<long long>
#define vvl vector<vector<long long>>

using namespace std;

typedef long long ll;

int main()
{
  int n;
  cin >> n;
  vi v_o(n / 2);
  vi v_e(n / 2);
  REP(i, n)
  {
    if (i % 2 == 0)
      cin >> v_e[i / 2];
    else
      cin >> v_o[i / 2];
  }

  sort(ALL(v_e));
  sort(ALL(v_o));

  int max_e = 0;
  int max_o = 0;
  int sec_e = 0;
  int sec_o = 0;
  int num_e = v_e[0];
  int num_o = v_o[0];

  int nc = 0;
  int ne = v_e[0];
  REP(i, n / 2)
  {
    if (v_e[i] == ne)
    {
      nc++;
      if (i == n / 2 - 1)
      {
        if (nc > max_e)
        {
          sec_e = max_e;
          max_e = nc;
          num_e = v_e[i - 1];
        }
        else if (sec_e < nc)
        {
          sec_e = nc;
        }
      }
    }
    else
    {
      if (nc > max_e)
      {
        sec_e = max_e;
        max_e = nc;
        num_e = v_e[i - 1];
      }
      else if (sec_e < nc)
      {
        sec_e = nc;
      }
      ne = v_e[i];
      nc = 1;
      if (i == n / 2 - 1 && sec_e < nc)
      {
        sec_e = nc;
      }
    }
  }
  nc = 0;
  int no = v_o[0];
  REP(i, n / 2)
  {
    if (v_o[i] == no)
    {
      nc++;
      if (i == n / 2 - 1)
      {
        if (nc > max_o)
        {
          sec_o = max_o;
          max_o = nc;
          num_o = v_o[i - 1];
        }
        else if (sec_o < nc)
        {
          sec_o = nc;
        }
      }
    }
    else
    {
      if (nc > max_o)
      {
        sec_o = max_o;
        max_o = nc;
        num_o = v_o[i - 1];
      }
      else if (sec_o < nc)
      {
        sec_o = nc;
      }
      no = v_o[i];
      nc = 1;
      if (i == n / 2 - 1 && sec_o < nc)
      {
        sec_o = nc;
      }
    }
  }
  int count;
  if (num_o == num_e)
  {
    if (max_o + max_e == n)
    {
      cout << n / 2 << endl;
      return 0;
    }
    int hoge = (n / 2 - max_o) + (n / 2 - sec_e);
    int fuga = (n / 2 - sec_o) + (n / 2 - max_e);
    count = min(hoge, fuga);
  }
  else
  {
    count = (n / 2 - max_o) + (n / 2 - max_e);
  }
  cout << count << endl;
  return 0;
}