#include <bits/stdc++.h>
using namespace std;
struct xxx
{
	int x,y,z;
}f[1000000005];
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);
		f[x].x++;
		f[y].x++;
		f[x].y++;
	}
	int m=(n+1)/2,b=0;
	for(int i=1;i<=n;i++)
	{
		if(f[i].x>=m)
		  b=1;
	}
	if(b==0)
	{
	  printf("Impossible");
      return 0;
	}
	int minn=1e9;
	for(int i=1;i<=n;i++)
	{
		if(f[i].x>=m)
		  f[i].z=m-f[i].y;
		else
		  f[i].z=1e9;
		minn=min(minn,f[i].z);
//		cout<<f[i].x<<' '<<f[i].y<<' '<<f[i].z<<endl;
	}
	printf("%d",minn);
	return 0;
}