#include <bits/stdc++.h>
using namespace std;
#define int long long
#define endl "\n"
#define PII pair<int,int>
#define PIS pair<int,string>
#define fr(i,x,y) for(int i=x,p=y;i<=p;i++)
#define rp(i,x,y) for(int i=x,p=y;i>=p;i--)
const int N=1e6+10;
const int M=1e2+10;
int mod=998244353;
int a[N],b[N];
int f[M][M];
void solve(){
	int n,m;
	cin>>n>>m;
	fr(i,1,n)cin>>a[i];
	fr(i,1,m)cin>>b[i];
	sort(a+1,a+n+1);
	sort(b+1,b+m+1);
	int maxa=0;
	fr(i,0,m-1){
		if(b[i+1]==b[i])continue;
		int l=b[i],r=b[i+1];
		auto t=upper_bound(a+1,a+1+n,l);
		auto q=lower_bound(a+1,a+1+n,r);
		maxa=max(maxa,(int)(q-t));
		
	}
	if(maxa==0){
		cout<<"Impossible"<<endl;
		return;
	}
	cout<<maxa<<endl;
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	int n=1;
	cin>>n;
	while(n--)
	solve();
	return 0;
}