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: Accepted)

#include <bits/stdc++.h>
#define fi first
#define se second
#define sz(x) ((int)(x).size())
using namespace std;

map<int,int> tr[2];
int n;

int main() {
    scanf("%d",&n);
    for(int i=0;i<n;i++) {
        int v;
        scanf("%d",&v);
        tr[i&1][v]+=1;
    }

    int m[2][2]={0,},t[2][2]={0,};
    int s=0;
    for(int i=0;i<2;i++) {
        int mx=0;
        for(auto &it:tr[i]) {
            if(m[i][0] < it.se) {
                t[i][1]=t[i][0]; t[i][0]=it.fi;
                m[i][1] = m[i][0]; m[i][0]=it.se;
            } else if(m[i][1]<it.se) {
                t[i][1]=it.fi;
                m[i][1]=it.se;
            }
        }
    }
    if(t[0][0]!=t[1][0]) printf("%d\n",n-(m[0][0]+m[1][0]));
    else printf("%d\n",n-max(m[0][0]+m[1][1], m[0][1]+m[1][0]));
    
    return 0;
}