#include <bits/stdc++.h>

using namespace std;

#define int128 __int128_t
#define int long long
#define PII pair<int, int>
#define PDD pair<double, double>
#define fi first    
#define se second
#define lowbit(x) x & -x
#define all(x) x.begin(), x.end()
#define INF 0x3f3f3f3f3f3f3f3f
#define ls(x) x << 1
#define rs(x) x << 1 | 1
#define ull unsigned long long
std::mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());

const int N = 1e6 + 10, M = 5e6 + 10, mod = 998244353;
const double eps = 1e-8;

int t, n, m, k;	
string sr;

void solve() {
	cin >> n >> m;
	vector<int> a(n), b(m);
	for (auto &x : a) cin >> x;
	for (auto &x : b) cin >> x;
	int res = 0, pos = 0, sum = 0;
	b.push_back(-INF), b.push_back(INF);
	sort(all(a)), sort(all(b));
	for (int i = 1; i <= m; i++) {
		while (pos < n && a[pos] < b[i]) {
			sum++;
			pos++;
		}
		res = max(res, sum);
		sum = 0;
		while (pos < n && a[pos] == b[i]) pos++;
	}
	if (res == 0) cout << "Impossible\n";
	else cout << res << "\n";
}

signed main() {
	cin.tie(nullptr)->sync_with_stdio(false);
	//cout.setf(ios::fixed), cout.precision(8);
	t = 1;
	cin >> t;
	while (t--) {
		solve();
	}
	return 0;
}