#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);
    if(a[0]>b[m-1]||a[n-1]<b[0])
    {
        cout<<n<<'\n';
        return ;
    }
    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;)
    {
        // cout << r << ' ' << k << ' ';
        // cout<<"\n";
        if (a[r]>=b[k])
        {    
            if (r < n - 1 && a[r] == a[r + 1])
                while (r < n - 1 && a[r] == a[r + 1])r++;
            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();
    }
}