#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,ans=N;

int main()
{
	scanf("%d", &n);
	for (int i=1; i<=n; i++)
	{
		int a,b;
		scanf("%d %d",&a, &b);
		if (a==b) M0[a]++;//¼Ç¼aµÄ´ÎÊý
		else M0[a]++, M1[b]++;
		A[++m]=a;//½«ËùÓгöÏÖµÄÊý¶¼·ÅÔÚA[]ÖÐ
		A[++m]=b;
	}
	sort(A+1,A+m+1);
	for (int i=1; i<=m; i++)//ö¾ÙÔÚ×îÖÕÒª·­µÄÅÆÃæÊý×Ö
	{
		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 0;
}