#include<bits/stdc++.h>
#define IOS ios::sync_with_stdio(false), cin.tie(0),cout.tie(0)
#define endl '\n'
#define PII pair<int,int>
#define int long long
//#define int __int128
using namespace std;
const int N = 2e5 + 10, M = 1e2 + 10, mod = 998244353, inf = 0x3f3f3f3f, base = 131;
const double eps = 1e-12;
void solve(){
    int n, m;
    cin >> n >> m;
    vector<int> a, b;
    for(int i = 0; i < n; i++){
        int x; cin >> x;
        a.push_back(x);
    }
    
    for(int i = 0; i < m; i++){
        int x; cin >> x;
        b.push_back(x);
    }
    a.push_back(-inf);
    a.push_back(inf);
    b.push_back(-inf);
    b.push_back(inf);
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    int ans = 0;
    for(int i = 1; i < m; ++ i){
        int pl = b[i], pr = b[i + 1];
        int l = upper_bound(a.begin(), a.end(), pl) - a.begin();
        int r = lower_bound(a.begin(), a.end(), pr) - a.begin();
        ans = max(ans, r - l);
    }
    if(ans) cout << ans << endl;
    else cout << "Impossible" << endl;
}
signed main()
{
    IOS;
    int T = 1;
    cin >> T;
    while (T--)
        solve();
}