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 <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); i++)
typedef long long ll;

int main() {
  int n;
  cin >> n;
  vector<ll> v(n), ve1(100003), ve2(100003);
  rep(i, n) cin >> v[i];

  int x1, x2, mx1 = 0, mx2 = 0;
  for (int i = 0; i < n; ++i) {
    if (i % 2 == 0) {
      ve1[v[i]]++;
      if (ve1[v[i]] > mx1) x1 = v[i], mx1 = ve1[v[i]];
    } else {
      ve2[v[i]]++;
      if (ve2[v[i]] > mx2) x2 = v[i], mx2 = ve2[v[i]];
    }
  }
  sort(ve1.rbegin(), ve1.rend());
  sort(ve2.rbegin(), ve2.rend());

  ll ans;
  if (x1 != x2) {
    ans = n - mx1 - mx2;
  } else {
    ans = n - max(mx1 + ve2[1], mx2 + ve1[1]);
  }

  cout << ans << endl;
}