#include<bits/stdc++.h>
using namespace std;
//\xb5÷\xd6\xcaǾ߱\xb8\xb6\xfe\xb7\xd6\xd0Եģ\xac\xb5\xab\xc8\xe7\xba\xcecheck\xa3\xbf

const int N=1e5+10;
int a[N],b[N];
int n,m;
void solve(){
	cin>>n>>m;
    for(int i=1;i<=n;i++) cin>>a[i];
    for(int j=1;j<=m;j++) cin>>b[j];
    sort(a+1,a+1+n);
    sort(b+1,b+1+m);
    b[m+1]=1e9+10;
    //\xbc\xc7¼ÿ\xb8\xf6b֮\xbc\xe4\xbcж\xe0\xc9ٸ\xf6a\xbc\xb4\xbfɣ\xa1\xa3\xa1\xa3\xa1
    int ans=0;
    int i=1,j=1;
    while(j<=m+1){
        int tmp=0;
        while(a[i]<b[j]&&a[i]>b[j-1]){
//        	cout<<i<<endl;
            i++;
            tmp++;
        }
        j++;
        if(a[i]==b[j-1]) i++;
        ans=max(tmp,ans);
    }
//    if(i<=n){
//        ans=max(ans,n-i+1);
//    }
//    cout<<(ans==0)?"Impossible":ans;
	if(ans==0) cout<<"Impossible";
	else cout<<ans;
	cout<<"\n";
}
int main(){
	int t;
	cin>>t;
	while(t--){
		solve();
	}
}