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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
#include<stdlib.h>

int compare (const void*a,const void*b)
{
    if(*(int*)a-*(int*)b>0) return 1;
    else if(*(int*)a-*(int*)b<0) return -1;
    return 0;
}

int cmp(int *a, int n)
{
  qsort(a,n,sizeof(int),compare); int count=1; int max =-1;
  for(int i=1;i<n;i++)
  {
      if(a[i]==a[i-1])
      {
          count++;
          if(max<count) max=count;
      }
      else count =1;
  }
  return (n-max);
}
int main()
{
    int n;
    scanf("%d",&n);
    
    int a[n],b[n/2],c[n/2];
    for (int i=0;i<n;i++) scanf("%d",a+i);
     int tmp =0;
    for(int i=0;i<n/2;i++)
    {
       b[i] = a[tmp*2+1];
       c[i] = a[tmp*2];
       tmp++;
    }
    if(cmp(c,n/2)==0&&cmp(b,n/2)==0&&a[1]==a[0]) printf("%d",n/2);
    else printf("%d",cmp(b,n/2)+cmp(c,n/2));
}