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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;

public class Main {

  public static void main(String[] args) {
    new Main().run();
  }

  public void run() {
    
    try(BufferedReader in = new BufferedReader(new InputStreamReader(System.in))) {

      int n = Integer.parseInt(in.readLine());
      String line = in.readLine();
      int nHalf = n >> 1;

      Integer num;
      Map<Integer,Integer> mapA = new HashMap<>();
      Map<Integer,Integer> mapB = new HashMap<>();;
      int offset=0,next=0;
      char regx = ' ';

      for(int i=0; i<n; i++) {
        if((next = line.indexOf(regx,offset)) == -1)
          next = line.length();
        num = new Integer(line.substring(offset, next));
        offset = ++next;

        // if((i&1) == 0)
        //   mapA.merge(num, 1, Integer::sum);
        // else
        //   mapB.merge(num, 1, Integer::sum);

        if((i & 1) == 0) {
          if(mapA.containsKey(num))
            mapA.replace(num, mapA.get(num) + 1);
          else
            mapA.put(num, 1);
        }
        else {
          if(mapB.containsKey(num))
            mapB.replace(num, mapB.get(num) + 1);
          else
            mapB.put(num, 1);
        }
      }

      int[] vm1 = {0,0};
      int[] vm2 = {0,0};
      int[] x   = {0,0};

      for (Map.Entry<Integer,Integer> m : mapA.entrySet()) {
        int val = m.getValue();
        if(vm1[0] <val) {
          vm2[0] = vm1[0];
          vm1[0] = val;
          x[0]  = m.getKey();
        } else if(vm2[0] < val) {
          vm2[0] = val;
        }
      }
      for (Map.Entry<Integer,Integer> m : mapB.entrySet()) {
        int val = m.getValue();
        if(vm1[1] <val) {
          vm2[1] = vm1[1];
          vm1[1] = val;
          x[1]  = m.getKey();
        } else if(vm2[1] < val) {
          vm2[1] = val;
        }
      }

      int ans = 0;
      int cca1 = nHalf - vm1[0];
      int ccb1 = nHalf - vm1[1];
      int cca2 = nHalf - vm2[0];
      int ccb2 = nHalf - vm2[1];

      if(x[0] == x[1])
        ans = cca2 > ccb2 ? cca1 + ccb2 : cca2 + ccb1;
      else
        ans = cca1 + ccb1;

      System.out.println(ans);
    }
    catch(IOException e) {
      System.err.println(e);
    }
  }
}