#include<bits/stdc++.h>
using namespace std;

const int N=300005;

int n,cnt=0;
int ans_cs,sum,m;
int a[N],b[N],c[2*N];

int main(){
	
//    freopen("card.in","r",stdin);
//    freopen("card.out","w",stdout);
    
    scanf("%d",&n);
    for(int i=1;i<=n;i++){	
		scanf("%d%d",&a[i],&b[i]);
		c[++cnt]=a[i];
    	if(a[i]!=b[i]) c[++cnt]=b[i];
  
    }
    sort(c+1,c+cnt+1);
    
	sum=0; 
	m=(n+1)/2;
    ans_cs=n+1;
    
	for(int i=1;i<=cnt;i++){
		
        if(c[i]==c[i-1]){
			
			sum++;
			if(sum==m){
                int cs=0;
                for(int j=1;j<=n;j++)  
				    if(a[j]==c[i]) cs++;
                cs=min(cs,m);
                ans_cs=min(ans_cs,m-cs);
			}   
			     
        }else{
            sum=1;
            if(sum==m){
            	ans_cs=0;
	            break;
			}   
		}
	}
	
	if(ans_cs>n) printf("Impossible");
    else printf("%d",ans_cs);
    
	return 0;

}