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 <iostream>
#include <vector>
#include <map>

using namespace std;

int main(){
  int N;
  cin >> N;
  vector<int> A(N);
  
  map<int, int> oddm, evenm;
  int oddc = 0, evenc = 0;
  int maxodd = 0, maxeven = 0;
  int maxv = 0;
  for(int i = 0; i < N; i++){
    cin >> A[i];
    maxv = max(A[i], maxv);
  }
  for(int i = 0; i < N; i += 2){
    oddm[A[i]]++;
  }
  for(int i = 1; i < N; i += 2){
    evenm[A[i]]++;
  }
  
  for(int i = 0; i <= maxv; i++){
    if(oddc < oddm[i]){
    oddc = oddm[i];
    maxodd = i;
    }
    if(evenc < evenm[i]){
    evenc = evenm[i];
    maxeven = i;
    }
  }
  
  if(maxeven != maxodd){
    cout << (N/2 - oddc) + (N/2 - evenc);
  }else if(oddc == N / 2 || evenc == N /2){
    cout << N / 2;
  }else {
    cout << N / 2 + min(N / 2 - oddc, N / 2 - evenc);
  }
}