#include <bits/stdc++.h>

using namespace std;

#define int128 __int128_t
#define int long long
#define PII pair<int, int>
#define PDD pair<double, double>
#define fi first    
#define se second
#define lowbit(x) x & -x
#define all(x) x.begin(), x.end()
#define INF 0x3f3f3f3f3f3f3f3f
#define ls(x) x << 1
#define rs(x) x << 1 | 1
#define ull unsigned long long
std::mt19937_64 rng(std::chrono::steady_clock::now().time_since_epoch().count());

const int N = 1e6 + 10, M = 5e6 + 10, mod = 998244353;
const double eps = 1e-8;

int t, n, m, k;	
string sr;

void solve() {
	int x, y;
	cin >> x >> y >> sr;
	map<char, int> mp;
	int ex = 0, ey = 0;
	for (auto it : sr) {
		mp[it]++;
		if (it == 'L') ex--;
		else if (it == 'R') ex++;
		else if (it == 'U') ey++;
		else ey--;
	}
	if ((x == 0 && y == 0) ||ex == x && ey == y) {
		cout << "Impossible\n";
		return;
	}

	auto check = [&](char s1, char s2) {
		int tx = ex, ty = ey;
		for (int j = 0; j < mp[s1]; j++) {
			if (s1 == 'L') tx++;
			else if (s1 == 'R') tx--;
			else if (s1 == 'U') ty--;
			else ty++;
			if (tx == x && ty == y) return false;
		}
		for (int j = 0; j < mp[s2]; j++) {
			if (s2 == 'L') tx++;
			else if (s2 == 'R') tx--;
			else if (s2 == 'U') ty--;
			else ty++;
			if (tx == x && ty == y) return false;
		}
		return true;
	};
	vector<char> ans;
	if (x > 0) {
		ans.push_back('L');
		if (y > 0) {
			ans.push_back('D');
			if (check('R', 'U')) {
				ans.push_back('U');
				ans.push_back('R');
			}
			else if (check('U', 'R')) {
				ans.push_back('R');
				ans.push_back('U');
			}
			else {
				cout << "Impossible\n";
				return;
			}
		}
		else {
			ans.push_back('U');
			if (check('R', 'D')) {
				ans.push_back('D');
				ans.push_back('R');
			}
			else if (check('D', 'R')) {
				ans.push_back('R');
				ans.push_back('D');
			}
			else {
				cout << "Impossible\n";
				return;
			}
		}
	}
	else {
		ans.push_back('R');
		if (y > 0) {
			ans.push_back('D');
			if (check('L', 'U')) {
				ans.push_back('U');
				ans.push_back('L');
			}
			else if (check('U', 'L')) {
				ans.push_back('L');
				ans.push_back('U');
			}
			else {
				cout << "Impossible\n";
				return;
			}
		}
		else {
			ans.push_back('U');
			if (check('L', 'D')) {
				ans.push_back('D');
				ans.push_back('L');
			}
			else if (check('D', 'L')) {
				ans.push_back('L');
				ans.push_back('D');
			}
			else {
				cout << "Impossible\n";
				return;
			}
		}
	}
	for (int i = 0; i < ans.size(); i++)
		for (int j = 0; j < mp[ans[i]]; j++)
			cout << ans[i];
	cout << "\n";
}

signed main() {
	cin.tie(nullptr)->sync_with_stdio(false);
	//cout.setf(ios::fixed), cout.precision(8);
	t = 1;
	cin >> t;
	while (t--) {
		solve();
	}
	return 0;
}