# include <bits/stdc++.h>
using namespace std;

# ifndef ONLINE_JUDGE
# include "debug.h"
# else
# define debug(...) 0721
# define ps 0721
# endif

using i32 = signed;
using i64 = long long;

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

    sort(a.begin(), a.end());
    sort(b.begin(), b.end());

    int ans = 0;
    {
        int it = lower_bound(a.begin(), a.end(), b[0]) - a.begin();
        ans = max(ans, it);

        it = a.end() - upper_bound(a.begin(), a.end(), b[m - 1]);
        ans = max(ans, it);
    }
    for(int i = 0; i < m - 1; ++i) {
        int it = lower_bound(a.begin(), a.end(), b[i + 1]) - upper_bound(a.begin(), a.end(), b[i]);
        ans = max(ans, it);
    }
    if(ans == 0) cout << "Impossible\n";
    else cout << ans << '\n';
}

i32 main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

    i32 t = 1;
    cin >> t;
    while (t --) {
        solve();
    }
    return 0;
}