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

const int maxn = 1e6 + 5;
map<char, int> mp, mp2;
string s;
char ans[maxn];
int cnt;


void solve()
{
	int x, y, ansx = 0, ansy = 0;
	cin >> x >> y;
	cin >> s;
	mp.clear();

	if (x == 0 && y == 0) {
		cout << "Impossible" << endl;
		return;
	}
	int flag = 0;
	for (int i = 0; i < s.size(); i++) {
		if (s[i] == 'U') {
			ansy++;
		}
		if (s[i] == 'D') {
			ansy--;
		}
		if (s[i] == 'L') {
			ansx--;
		}
		if (s[i] == 'R') {
			ansx++;
		}
		if (ansx == x && ansy == y) {
			flag = 1;
		}
	}
//cout << ansx << " " << ansy << endl;
	if ((x != ansx || y != ansy)&&flag != 1) {
		cout << s << endl;
		return;
	}
	for (int i = 0; i < s.size(); i++) {
		mp[s[i]]++;
	}

	if ((mp['U'] == 0 && mp['D'] == 0)) {
		if (x >= 0) {
			if (mp['L'] > mp['R']) {  //先左后右
				for (int i = 1; i <= mp['L']; i++) {
					cout << "L";
				}
				for (int i = 1; i <= mp['R']; i++) {
					cout << "R";
				}
				cout << endl;
				return;
			}
			else if (mp['L'] == mp['R']) {
				cout << "Impossible" << endl;
				return;
			}
			else {
				if (mp['R'] - mp['L'] >= x) {
					cout << "Impossible" << endl;
					return;
				}
				else { // 先左
					for (int i = 1; i <= mp['L']; i++) {
						cout << "L";
					}
					for (int i = 1; i <= mp['R']; i++) {
						cout << "R";
					}
					cout << endl;
					return;
				}
			}
		}
		else {
			if (mp['L'] <= mp['R']) {  //先右
				for (int i = 1; i <= mp['R']; i++) {
					cout << "R";
				}
				for (int i = 1; i <= mp['L']; i++) {
					cout << "L";
				}
				cout << endl;
				return;
			}
			else {
				if (mp['R'] - mp['L'] <= x) {
					cout << "Impossible" << endl;
					return;
				}
				else { // 先右
					for (int i = 1; i <= mp['R']; i++) {
						cout << "R";
					}
					for (int i = 1; i <= mp['L']; i++) {
						cout << "L";
					}
					cout << endl;
					return;
				}
			}
		}

	}


	if ((mp['L'] == 0 && mp['R'] == 0)) {
		if (y >= 0) {
			if (mp['D'] > mp['U']) {  //先左后右
				for (int i = 1; i <= mp['D']; i++) {
					cout << "D";
				}
				for (int i = 1; i <= mp['U']; i++) {
					cout << "U";
				}
				cout << endl;
				return;
			}
			else if (mp['D'] == mp['U']) {
				cout << "Impossible" << endl;
				return;
			}
			else {
				if (mp['U'] - mp['D'] >= y) {
					cout << "Impossible" << endl;
					return;
				}
				else { // 先左
					for (int i = 1; i <= mp['D']; i++) {
						cout << "D";
					}
					for (int i = 1; i <= mp['U']; i++) {
						cout << "U";
					}
					cout << endl;
					return;
				}
			}
		}
		else {
			if (mp['D'] <= mp['U']) {  //先右
				for (int i = 1; i <= mp['U']; i++) {
					cout << "U";
				}
				for (int i = 1; i <= mp['D']; i++) {
					cout << "D";
				}
				cout << endl;
				return;
			}
			else {
				if (mp['U'] - mp['D'] <= y) {
					cout << "Impossible" << endl;
					return;
				}
				else { // 先右
					for (int i = 1; i <= mp['U']; i++) {
						cout << "U";
					}
					for (int i = 1; i <= mp['D']; i++) {
						cout << "D";
					}
					cout << endl;
					return;
				}
			}
		}

	}


	cnt = 0;

	int dx = 0, dy = 0;
	dy += mp['U'];
	dy -= mp['D'];
	dx += mp['R'];
	dx -= mp['L'];
	if (dx == x && dy == y) {
		cout << "Impossible" << endl;
		return;
	}

	if (x >= 0) {
		for (int i = 1; i <= mp['L']; i++) {
			ans[++cnt] = 'L';
		}
	}
	else {
		for (int i = 1; i <= mp['R']; i++) {
			ans[++cnt] = 'R';
		}
	}
	if (y >= 0) {
		for (int i = 1; i <= mp['D']; i++) {
			ans[++cnt] = 'D';
		}
	}
	else {
		for (int i = 1; i <= mp['U']; i++) {
			ans[++cnt] = 'U';
		}
	}

	if (x >= 0) {
		for (int i = 1; i <= mp['R']; i++) {
			ans[++cnt] = 'R';
		}
	}
	else {
		for (int i = 1; i <= mp['L']; i++) {
			ans[++cnt] = 'L';
		}
	}
	if (y >= 0) {
		for (int i = 1; i <= mp['U']; i++) {
			ans[++cnt] = 'U';
		}
	}
	else {
		for (int i = 1; i <= mp['D']; i++) {
			ans[++cnt] = 'D';
		}
	}

	for (int i = 1; i <= cnt; i++) {
		cout << ans[i];
	}
	cout << endl;

}

signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0); cout.tie(0);

	int t = 1;
	cin >> t;
	while (t--) {
		solve();
	}

	return 0;
}