#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;

const int N = 1e5 + 10;
#define int long long
int a[N], b[N];
int n, m;
int mx = 0;
int ans = 0;


void solve()
{
	cin >> n >> m;
	for (int i = 0; i < n; i++)cin >> a[i];
	for (int j = 0; j < m; j++)cin >> b[j];

	sort(a, a + n);
	sort(b, b + m);
	ans = 0;
	bool ok = 0;
	if (n == m)
	{
		for (int i = 0; i < n; i++)
		{
			if (a[i] != b[i]) {
				ok = 1;
				break;
			}
		}
	}
	if (!ok&&n==m)
	{
		cout << "Impossible" << endl;
		return;
	}

	int k = 0;
	mx = 0;
	int l, r;
	for (l = 0, r = 0; l < n && r < n;)
	{
		
		if (a[r]>=b[k])
		{	
			int xx = 0;
			if (r < n - 1 && a[r] == a[r + 1])
				while (r < n - 1 && a[r] == a[r + 1])xx++,r++;
			if (a[r] != b[k])ans = max(ans, xx+1);
			r++;
			l = r;
			if(k<m-1&&b[k+1]==b[k])
				while (k < m - 1 && b[k] == b[k + 1])k++;
			if (k < m - 1)k++;
			ans = max(ans, mx);
			mx = 1;
			//cout << r << ' ' << k << endl;
		}
		else if (a[r]<b[k])
		{
			//cout << r << endl;
			r++;
			mx++;
		}
		//cout << l << ' ' << r << endl;
	}
	if (r != l) {
		if (l > 0)
			ans = max(ans, r - l + 1);
		else ans = max(ans, r - l);
	}
	cout << ans << endl;
}

signed main()
{
	int T;
	cin >> T;
	while (T--)
	{
		solve();
	}
}