#include<bits/stdc++.h>
using namespace std;
int n,l,cnt,need,maxx,x[300010],y[300010];
int b[700010],c[700010],d[30],e[30];
bool v[1000000010];
int main()
{
//	freopen("card.in","r",stdin);
//	freopen("card.out","w",stdout);
	scanf("%d",&n);
	need=(n+1)/2;
	for (int i=1;i<=n;i++) {
		scanf("%d%d",&x[i],&y[i]);
		if (!v[x[i]]) {
			v[x[i]]=1;
			b[++cnt]=x[i];
			c[cnt]=1;
			if (1>=maxx) {
			   	if (1==maxx) l++;
				else l=1;
				d[l]=x[i];
			 	maxx=1;
			}
		}
		else {
			for (int j=1;j<=cnt;j++)
			    if (b[j]==x[i]) {
			    	c[j]++;
			    	if (c[j]>=maxx) {
			    		if (c[j]==maxx) l++;
						else l=1;
						d[l]=x[i];
			    		maxx=c[j];
					}
			    	break;
				}
		}
		if (!v[y[i]]) {
			v[y[i]]=1;
			b[++cnt]=y[i];
			c[cnt]=1;
			if (1>=maxx) {
			   	if (1==maxx) l++;
				else l=1;
				d[l]=y[i];
			 	maxx=1;
			}
		}
		else {
			for (int j=1;j<=cnt;j++)
			    if (b[j]==y[i]) {
			    	c[j]++;
			    	if (c[j]>=maxx) {
			    		if (c[j]==maxx) l++;
						else l=1;
						d[l]=y[i];
			    		maxx=c[j];
					}
			    	break;
				}
		}
	}
	if (maxx<need) {
		puts("Impossible");
		return 0;
	}
	maxx=0;
	for (int i=1;i<=n;i++)
	    for (int j=1;j<=l;j++)
	        if (x[i]==d[j]) {
	        	e[j]++;
	        	maxx=max(maxx,e[j]);
			}
	printf("%d",max(0,need-maxx));
}