#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <algorithm>
#include <bits/stdc++.h>
using namespace std;

const int N=300005;

map<int,int> M0,M1;
int A[2*N];
int n,m,a[N],b[N],ans=N;

void init()
{
	scanf("%d", &n);
	for (int i=1; i<=n; i++)
	{
		scanf("%d %d",&a[i], &b[i]);
		if (a[i]==b[i]) M0[a[i]]++;//记录a的次数
		else M0[a[i]]++, M1[b[i]]++;
		A[++m]=a[i];//将所有出现的数都放在A[]中
		A[++m]=b[i];
	}
	sort(A+1,A+m+1);
} 

void work()
{
	for (int i=1; i<=m; i++)//枚举在最终要翻的牌面数字
	{
		int x=M0[A[i]],y=M1[A[i]];
		if (x+y>=(n+1)/2)
			ans=min(ans,max((n+1)/2-x,0));
	}
	if (ans==N)printf("Impossible\n");
	else printf("%d\n",ans);
	return;
}

int main()
{
	init();
	work();
	return 0;
}