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;
  scanf("%d", &N);
  int v[N];
  vector<int> A,B;
  int testa[100000];
  int testb[100000];
  for (int i = 0; i < 100001; ++i) testa[i] = 0;
  for (int i = 0; i < 100001; ++i) testb[i] = 0;
  
  for (int i = 0; i < N; ++i) {
    scanf("%d", &v[i]);
    if(i%2==0){
      A.push_back(v[i]);
      ++testa[v[i]];
    }
    else{
      B.push_back(v[i]);
      ++testb[v[i]];
    }
  }

  int maxa=0;
  int nexta=0;
  int maxb=0; 
  int nextb = 0;
  for (int i = 0; i < 100001; ++i){
    if(testa[maxa]<testa[i]){
      nexta = maxa;
      maxa = i;
    }
    if(testb[maxb]<testb[i]){
      nextb = maxb;
      maxb = i;
    }
  }


  //cout << maxa << endl;
  //cout << maxb << endl;
  //cout << nexta << endl;
  //cout << nextb << endl;




  bool flip = true;
  int count = 0;
  int ans = 0;

  if(maxa==maxb){
    for (int i = 0; i < N; ++i){
      if(flip){
        if(v[i]!=nexta) ++count;
        flip = false;
      }
      else{
        if(v[i]!=maxb) ++count;
        flip = true;
      }
    }
    ans = count;
    count = 0;
    flip = true;
    for (int i = 0; i < N; ++i){
      if(flip){
        if(v[i]!=maxa) ++count;
        flip = false;
      }
      else{
        if(v[i]!=nextb) ++count;
        flip = true;
      }
    }
    if(count<ans) ans = count;
  }



  else{

  for (int i = 0; i < N; ++i){
    if(flip){
      if(v[i]!=maxa) ++ans;
      flip = false;
    }
    else{
      if(v[i]!=maxb) ++ans;
      flip = true;
    }
  }

  }

  cout << ans << endl;


}