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 ;
#define ll long long 
#define all(x) x.begin() , x.end()

int const N = 1000000;
int n , an , v[N],vis[N],cnt , freq1[N] , freq2[N];
vector<int>vv , g;
int main(){
    scanf("%d",&n);
    for(int i=0;i<n;++i){
        scanf("%d",v+i);
        if(!vis[v[i]])
        ++cnt,vis[v[i]]=1;
        if(i % 2)vv.push_back(v[i]);
        if(i % 2 == 0)g.push_back(v[i]);
    }
    if(cnt == 1){
        cout << n/2<<"\n";
        return 0 ; 
    }
    int sz = 0 , mx = 0 , mxx = 0;
   for(int i=0;i<vv.size();++i){
       if(!freq1[vv[i]])++sz;
       ++freq1[vv[i]];
       ++freq2[g[i]];
       mx = max(mx , freq1[vv[i]]);
       mxx = max(mxx,freq2[g[i]]);
   }
   an += n/2 - mx ;
   an += n/2 - mxx ; 
   cout << an << "\n";
}