#include <utility>
#include <cstdio>
#include <cmath>
#include <map>

typedef std::pair<unsigned int,unsigned int> count;

std::map<unsigned int,count> c;

int main()
{
	int n;
	scanf("%d",&n);
	for(int i=0;i<n;i++)
	{
		int a,b;
		scanf("%d%d",&a,&b);
		c[a].first++;
		if(a!=b)
		{
			c[b].first++;
			c[b].second++;
		}
	}
	unsigned int min=0xfffffffe;
	unsigned int need=(n+1)>>1;
	for(std::map<unsigned int,count>::iterator i=c.begin();i!=c.end();i++)
		if((i->second).first>=need)
			min=std::min(min,std::max(0U,need-(i->second).first+(i->second).second));
	if(min==0xfffffffe) puts("Impossible");
	else printf("%u\n",min);
	return 0;
}