#include <bits/stdc++.h>
using namespace std;
map<int,int>f1;
map<int,int>f2;
map<int,int>f3;
int n;
int main()
{
//    freopen("card.in","r",stdin);
//    freopen("card.out","w",stdout);
	int x,y;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	{
		scanf("%d %d",&x,&y);
		f1[x]++;
		f1[y]++;
		f2[x]++;
	}
	int m=(n+1)/2,b=0;
	for(int i=1;i<=n;i++)
	{
		if(f1[i]>=m)
		  b=1;
	}
	if(b==0)
	{
	  printf("Impossible");
      return 0;
	}
	int minn=1e9;
	for(int i=1;i<=n;i++)
	{
		if(f1[i]>=m)
		  f3[i]=m-f2[i];
		else
		  f3[i]=1e9;
		minn=min(minn,f3[i]);
//		cout<<f[i].x<<' '<<f[i].y<<' '<<f[i].z<<endl;
	}
	printf("%d",minn);
	return 0;
}