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: Runtime Error)


#include <iostream>
#include <vector>
using namespace std;
int mode (vector<int> v){//function mode
    int b[256]={0};
    int mode=0;
    long l=v.size();
    for (int i=0; i<l; i++) {
        b[v[i]]++;
    }
    for (int i=0; i<l; i++) {
        if (b[v[i]]>mode) {
            mode=v[i];
        }
    }
    return mode;
}

int second_mode(vector<int> v,int max){
    int b[256]={0};
    int mode=0;
    long l=v.size();
    for (int i=0; i<l; i++) {
        b[v[i]]++;
    }
    for (int i=0; i<l; i++) {
        if (b[v[i]]>mode) {
            if (v[i]!=max) {
                mode=v[i];
            }
        }
    }
    return mode;
}

int main() {
    int n;
    cin >> n;
    vector<int> ak;//奇数番目
    vector<int> ag;//偶数番目
    for (int i=0; i<n; i++) {
        int x;
        cin >> x;
        if (i%2==0) {
            ak.push_back(x);
        }else{
            ag.push_back(x);
        }
    }
    
    int modeAK=mode(ak);
    int modeAG=mode(ag);
    int cn=0;
    if (modeAK!=modeAG) {
        for (int i=0; i<n/2; i++) {
            if (ak[i]!=modeAK) {
                cn++;
            }
            if (ag[i]!=modeAG) {
                cn++;
            }
        }
    }else{
        int pt1=0,pt2=0;
        int secmodeAK=second_mode(ak, modeAK);
        int secmodeAG=second_mode(ag, modeAG);
        
        for (int i=0; i<n/2; i++) {
            if (ak[i]!=modeAK) {
                pt1++;
            }
            if(ag[i]!=secmodeAG){
                pt1++;
            }
        }
        for (int i=0; i<n/2; i++) {
            if (ak[i]!=secmodeAK) {
                pt2++;
            }
            if (ag[i]!=modeAG) {
                pt2++;
            }
        }
        cn=min(pt1, pt2);
    }
    cout<<cn<<endl;
    return 0;
}