#include<bits/stdc++.h>
#define int long long

using namespace std;

const int N = 1e5 + 7;
int n,m,k;
int a[N],b[N];

void solve(){
	cin >> n >> m;
	for(int i = 1;i <= n;i ++) cin >> a[i];
	for(int i = 1;i <= m;i ++) cin >> b[i];
	b[0] = 0,b[m + 1] = 1e9;
	sort(a + 1,a + 1 + n),sort(b + 1,b + 1 + m);
	int ans = 0;
	for(int i = 0;i <= m;i ++){
		int l = upper_bound(a + 1,a + 1 + n,b[i]) - a;
		int r = lower_bound(a + 1,a + 1 + n,b[i + 1]) - a - 1;
		ans = max(ans,r - l + 1);
	} if(ans) cout << ans << endl;
	else cout << "Impossible" << endl;
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr),cout.tie(nullptr);
	int _; cin >> _;
	while(_ --){
		solve();
	} return 0;
}