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 <algorithm>
#include <iostream>
#include <map>
#include <queue>
#include <vector>
using namespace std;

#define FOR(i, j, k) for (int i = j; i < k; i++)
#define REP(i, j) FOR(i, 0, j)
typedef long long int ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vi> vvi;

int main() {

  int n;
  cin >> n;
  vi v(n);
  REP(i, n) cin >> v[i];

  map<int, int> a1;
  map<int, int> a2;

  for (int i = 0; i < n; i += 2) {
    a1[v[i]]++;
  }
  for (int i = 1; i < n; i += 2) {
    a2[v[i]]++;
  }

  vector<pii> b1, b2;

  for (auto p : a1) {
    b1.push_back(make_pair(p.second, p.first));
  }
  for (auto p : a2) {
    b2.push_back(make_pair(p.second, p.first));
  }

  sort(b1.begin(), b1.end());
  sort(b2.begin(), b2.end());

  auto x1 = b1[b1.size() - 1];
  pii x2;
  if (b1.size() > 1)
    x2 = b1[b1.size() - 2];
  else
    x2 = make_pair(0, 0);

  auto y1 = b2[b2.size() - 1];
  pii y2;
  if (b2.size() > 1)
    y2 = b2[b2.size() - 2];
  else
    y2 = make_pair(0, 0);

  if (x1.second != y1.second)
    cout << n - x1.first - y1.first << endl;
  else {
    if (x1.first > y1.first) {
      cout << n - x1.first - y2.first << endl;
    } else if (y1.first > x1.first) {
      cout << n - x2.first - y1.first << endl;
    } else {
      cout << n - x1.first - max(x2.second, y2.second) << endl;
    }
  }

  return 0;
}