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>
#define rep(i,x,y) for (int i=(x);i<=(y);i++)
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
const int N=1e5+5;
int n,a[N],q[N],cnt[N],top,topx,topy,ans; pii x[N],y[N];
int main(){
	scanf("%d",&n);
	rep (i,1,n) scanf("%d",&a[i]);
	for (int i=1;i<=n;i+=2) q[++top]=a[i],cnt[a[i]]++;
	topx=unique(q+1,q+1+top)-q-1;
	rep (i,1,topx) x[i]=pii(cnt[q[i]],q[i]); x[++topx]=pii(0,-1);
	sort(x+1,x+1+topx,greater<pii>());
	top=0; memset(cnt,0,sizeof(cnt));
	for (int i=2;i<=n;i+=2) q[++top]=a[i],cnt[a[i]]++;
	topy=unique(q+1,q+1+top)-q-1;
	rep (i,1,topy) y[i]=pii(cnt[q[i]],q[i]); y[++topy]=pii(0,-2);
	sort(y+1,y+1+topy,greater<pii>());
	rep (i,1,2) rep (j,1,2) if (x[i].se!=y[j].se) ans=max(ans,x[i].fi+y[j].fi);
	cout<<n-ans;
	return 0;
}