#define _CRT_SECURE_NO_WARNINGS
#define itn int
#define PII pair<int, int>
#define PLI pair<long long, int>
#define fep(i, a, b) for(int i = (a); i >= (b); --i)
#define rep(i, a, b) for(int i = (a); i <= (b); ++i)
#include<bits/stdc++.h>
#include<unordered_map>
using ll = long long;
using ldou = long double;
using unll = unsigned long long;
using namespace std;

inline int read() {
	int x = 0, f = 1;
	char ch = getchar();
	while (!isdigit(ch)) { f = ch != '-'; ch = getchar(); }
	while (isdigit(ch)) { x = (x << 1) + (x << 3) + (ch ^ 48); ch = getchar(); }
	return f ? x : -x;
}

ll gcd(ll a, ll b) { // 最大公约数
	while (b ^= a ^= b ^= a %= b)
		;
	return a;
}
ll lcm(ll a, ll b) { // 最小公倍数
	return a / gcd(a, b) * b;
}
ll qmi(ll m, ll k, ll p) { // 快速幂
	//求 m^k mod p，时间复杂度 O(logk)。
	//m为底数，k为幂
	ll res = 1 % p, t = m;
	while (k) {
		if (k & 1) res = res * t % p;
		t = t * t % p;
		k >>= 1;
	}
	return res;
}
unll qmi(unll m, unll k, unll p) { //龟速乘
	ll res = 0, t = m;
	while (k) {
		if (k & 1) res = (res + t) % p;
		k >>= 1;
		t = (t << 1) % p;
	}
	return res;
}

////////////////////////////////////////////////////////////////////////////////

ll n, m, k;
const int N = 1000010;
const int M = 2e5 + 50;
const ll INF = 0x3f3f3f3f;
const ll MODE = ll(998244353);
const double Pi = 3.1415926;
const double eps = 1e-8;
const int dx[4] = { 1,-1, 0, 0 };
const int dy[4] = { 0, 0, 1,-1 };
//priority_queue<int> p;//这是一个大根堆q
//priority_queue<int, vector<int>, greater<int> >q;//这是一个小根堆q
//priority_queue<ll, vector<ll>, greater<ll> >pq; // 小根

ll a[5];
string str;

void solve() {

	ll edx = 0, edy = 0;
	ll x, y;
	cin >> x >> y;
	
	cin >> str;
	memset(a, 0, sizeof(a));

	for (int i = 0; i < str.size(); i++)
	{
		if (str[i] == 'U') a[0]++;
		if (str[i] == 'D') a[1]++;
		if (str[i] == 'L') a[2]++;
		if (str[i] == 'R') a[3]++;
	}

	edx = a[3] - a[2];
	edy = a[0] - a[1];

	if (x == 0 && y == 0) {
		cout << "Impossible" << '\n';
		return;
	}
	else if (edy == y && edx == x) {
		cout << "Impossible" << '\n';
		return;
	}
	else if (a[2] == 0 && a[3] == 0)
	{
		if (x != 0) {
			cout << str << '\n';
			return;
		}
		else {
			if (y > edy && y >= 0) {
				for (int i = 0; i < a[1]; i++)cout << 'D';
				for (int i = 0; i < a[0]; i++)cout << 'U';
				cout << '\n';
				return;
			}
			else if (y <= 0 && edy <= y)
			{
				cout << "Impossible" << '\n';
				return;
			}
			else if (edy >= 0 && edy >= y && y >= 0)
			{
				if (0 <= y) {
					cout << "Impossible" << '\n';
					return;
				}
				else {
					for (int i = 1; i <= a[0]; i++) cout << 'U';
					for (int i = 1; i <= a[1]; i++) cout << 'D';
					cout << '\n';
					return;
				}
			}
			/*else if (edy >= 0 && edy >= y)
			{
				for (int i = 1; i <= a[0]; i++) cout << 'U';
				for (int i = 1; i <= a[1]; i++) cout << 'D';
				cout << '\n';
				return;
			}*/
			else if (y < edy && edy <= 0) {
				for (int i = 1; i <= a[0]; i++) cout << 'U';
				for (int i = 1; i <= a[1]; i++) cout << 'D';
				cout << '\n';
				return;
			}
			else {
				cout << "Impossible" << '\n';
				return;
			}
		}
		
		
	}
	else if (a[0] == 0 && a[1] == 0)
	{
		if (y != 0) {
			cout << str << '\n';
			return;
		}
		else {
			if (x <= 0 && edx <= x)
			{
				cout << "Impossible" << '\n';
				return;
			}
			else if (edx >= 0 && edx >= x && x >= 0) {
				if (0 <= x) {
					cout << "Impossible" << '\n';
					return;
				}
				else {
					for (int i = 1; i <= a[3]; i++) cout << 'R';
					for (int i = 1; i <= a[2]; i++) cout << 'L';
					cout << '\n';
					return;
				}
			}
			else if (x > edx && x >= 0) {
				for (int i = 1; i <= a[2]; i++) cout << 'L';
				for (int i = 1; i <= a[3]; i++) cout << 'R';
				cout << '\n';
			}
			/*else if (edx >= 0 && edx >= x)
			{
				for (int i = 1; i <= a[3]; i++) cout << 'R';
				for (int i = 1; i <= a[2]; i++) cout << 'L';
				cout << '\n';
				return;
			}*/
			else if (edx <= 0 && edx > x) {
				for (int i = 1; i <= a[3]; i++) cout << 'R';
				for (int i = 1; i <= a[2]; i++) cout << 'L';
				cout << '\n';
				return;
			}
			else {
				cout << "Impossible" << '\n';
				return;
			}
		}
	}
	else {
		if (edx == x)
		{
			if (x == 0) {
				if (a[2] != 0) {
					cout << 'L';
					--a[2];
				}
				else if (a[3] != 0) {
					cout << 'R';
					--a[3];
				}
				for (int i = 0; i < a[0]; i++) cout << "U";
				for (int i = 0; i < a[1]; i++) cout << "D";
				for (int i = 0; i < a[2]; i++) cout << "L";
				for (int i = 0; i < a[3]; i++) cout << "R";
				cout << '\n';
				return;
			}
			else {
				for (int i = 0; i < a[0]; i++) cout << "U";
				for (int i = 0; i < a[1]; i++) cout << "D";
				for (int i = 0; i < a[2]; i++) cout << "L";
				for (int i = 0; i < a[3]; i++) cout << "R";
				cout << '\n';
				return;
			}

		}
		else if (edy == y)
		{
			if (y == 0)
			{
				if (a[0] != 0) {
					cout << 'U';
					--a[0];
				}
				else if (a[1] != 0) {
					cout << 'D';
					--a[1];
				}
				for (int i = 0; i < a[2]; i++) cout << "L";
				for (int i = 0; i < a[3]; i++) cout << "R";
				for (int i = 0; i < a[0]; i++) cout << "U";
				for (int i = 0; i < a[1]; i++) cout << "D";
				cout << '\n';
				return;
			}
			else
			{
				for (int i = 0; i < a[2]; i++) cout << "L";
				for (int i = 0; i < a[3]; i++) cout << "R";
				for (int i = 0; i < a[0]; i++) cout << "U";
				for (int i = 0; i < a[1]; i++) cout << "D";
				cout << '\n';
				return;
			}
		}
		else
		{
			if (x == 0) {
				for (int i = 0; i < a[2]; i++) cout << "L";
				for (int i = 0; i < a[3]; i++) cout << "R";
				for (int i = 0; i < a[0]; i++) cout << "U";
				for (int i = 0; i < a[1]; i++) cout << "D";
				cout << '\n';
				return;
			}
			else {
				for (int i = 0; i < a[0]; i++) cout << "U";
				for (int i = 0; i < a[1]; i++) cout << "D";
				for (int i = 0; i < a[2]; i++) cout << "L";
				for (int i = 0; i < a[3]; i++) cout << "R";
				cout << '\n';
				return;
			}

		}
	}
	

}
signed main() {
	std::ios::sync_with_stdio(false); std::cin.tie(0), std::cout.tie(0);
	/*freopen("out.txt", "r", stdin);
	freopen("wrt.txt", "w", stdout);*/
	int TTT = 1; cin >> TTT;
	while (TTT--) {
		solve();
	}
	/*while (cin >> n >> m) {
		solve();
	}*/

	return 0;
}