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;
typedef long long ll;

#define rep(i,n) for(int i=0;i<(int)(n);i++)

/*Solve*/

int main(){
    ll n;
    vector<ll> ai,aj;
    cin >> n;
    map<ll,ll> mpi,mpj;
    ll maxi=0,maxj=0;
    
    vector<ll> v;
    rep(i,n){
        ll x;
        cin >> x;
        v.push_back(x);
    }
    
    ll tmpe[2];
    for(int i=0;i<n;i+=2){
        mpi[v[i]]++;
        if(maxi<mpi[v[i]]){
            maxi++;
            if(v[i]!=tmpe[0])tmpe[1]=tmpe[0];
            tmpe[0]=v[i];
        }
    }
    ll tmpo[2];
    bool flg=false;
    for(int i=1;i<n;i+=2){
        if(v[i]!=tmpe[0]){
            if(maxi==maxj)
                flg=true;
            mpj[v[i]]++;
            if(maxj<mpj[v[i]]){
                if(v[i]!=tmpo[0])tmpo[1]=tmpo[0];
                maxj++;
                tmpo[0]=v[i];
            }
        }else if(maxi==maxj)
            flg=true;
    }
    
    if(flg==true){
        ll x,y;
        x=n-(maxi+maxj);
        maxi=0;maxj=0;
        map<ll,ll> mp1,mp2;
        for(int i=0;i<n;i+=2){
            if(v[i]!=tmpo[0]){
                mp1[v[i]]++;
                if(maxi<mp1[v[i]]){
                    maxi++;
                }
            }
        }
        for(int i=1;i<n;i+=2){
            if(v[i]!=tmpe[1]){
                mp2[v[i]]++;
                if(maxj<mp2[v[i]]){
                    maxj++;
                }
            }
        }
        y=n-(maxi+maxj);
        cout << min(x,y);
        return 0;
    }
    
    cout << n-(maxi+maxj);
    
}