#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define mk make_pair
#define S second
#define F first
#define int long long
void solve(){
    int n,m;
    cin>>n>>m;
    vector<pair<int,int>> v;
    int a[n], b[m];
    set<int> s;
    for(int i=0; i<n; i++){
        cin>>a[i];
        //if(s.count(a[i])) continue;
        //pisda++;
        //v.push_back({a[i],1});
    }
    for(int i=0; i<m; i++){
        cin>>b[i];
        //v.push_back({b[i],2});
        //s.insert(b[i]);
    }
    int pisda=0;
    for(int i=0; i<m; i++){
        //cin>>b[i];
        v.push_back({b[i],2});
        s.insert(b[i]);
    }
    for(int i=0; i<n; i++){
        //cin>>a[i];
        if(s.count(a[i])) continue;
        pisda++;
        v.push_back({a[i],1});
    }
    if(pisda==0){
        cout<<"Impossible"<<endl;
        return;
    }
    int str=0;
    int ans=0;
    sort(v.begin(),v.end());
    for(pair<int,int> i: v){
           // cout<<i.first<<" "<<i.second<<endl;
        if(i.second==1){
            str++;
            ans=max(ans,str);
        }
        else{
            str=0;
        }
    }
    cout<<ans<<endl;
}
signed main(){
    int t;
    cin>>t;
    while(t--) solve();
}