#include <bits/stdc++.h>
#define int long long
#define endl '\n'
#define pii pair<int, int>
#define fr(i, a, b) for (int(i) = (a); (i) <= (b); (i)++)
#define br(i, a, b) for (int(i) = (a); (i) >= (b); (i)--)
#define PI acos(-1)
using namespace std;

int n, m;
const int maxn = 1e5 + 3;
int ans = 0;

void solve()
{
    cin >> n >> m;
    vector<int> a(n);
    vector<int> b(m);
    fr(i, 0, n - 1)
    {
        cin >> a[i];
    }
    fr(i, 0, m - 1)
    {
        cin >> b[i];
    }
    sort(a.begin(), a.end());
    sort(b.begin(), b.end());
    int ans = 0;
    int j = 0;
    fr(i, 0, n-1)
    {
        if(a[i] >= b[0])
        {
            j = i;
            break;
        }
        ans++;
    }
    fr(i, 0, m-2)
    {
        auto t = upper_bound(a.begin(), a.end(), b[i]) - a.begin();
        int cnt = 0;
        for(j = t; j < n; j++)
        {
            if(a[j] >= b[i+1])
            {
                break;
            }
            cnt++;
        }
        ans = max(ans, cnt);
    }
    int cnt = 0;
    for(; j < n; j++)
    {
        if(a[j] > b[m-1])
            cnt++;
    }
    if(ans == 0)
        cout<<"Impossible"<<endl;
    else
        cout << max(ans, cnt) << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);
    int T;
    //T = 1;
    cin >> T;
    while (T--)
    {
        solve();
    }
}