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 rep(i, n) for (int i = 0; i < (int)(n); i++)
using ll=long long;
using vi = vector<int>;
using Graph = vector<vi>;
using P = pair<int,int>;
const int MOD=(int)1e9+7;
const int INF=(int)1e9;
const ll LINF=(ll)1e18;

const int ten = 100000;

int main(){
    int n;cin>>n;
    map<int,int> odd,even;
    rep(i,n){
        int a;
        cin >> a;
        if(i%2==0) even[a]++;
        else odd[a]++;
    }
    int ema=0,ema2=0,oma=0,oma2=0;
    int oi,ei;
    rep(i,ten){
        if(ema<even[i]){
            ema2 = ema;
            ema = even[i];
            ei = i;
        }
    }
    rep(i,ten){
        if(oma<odd[i]){
            oma2 = oma;
            oma = odd[i];
            oi = i;
        }
    }
    int ans = n - ema - oma;
    if(oi==ei){
        ans = min(n - ema - oma2,n - ema2 - oma);
    }
    cout << ans << endl;
}