#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e6 + 10;
int x, y;
string s;
int flag = 0;
int dir[5];
int ds[4] = { 1, 2, 3, 4 };
char dp[5] = { '0', 'R', 'L', 'U', 'D' };

bool check() {
	int x1 = 0, y1 = 0;
	
	if (x == 0 && y == 0)return false;
	for (int i = 0; i <= 3; i++) {
		if (ds[i] == 1) {
			if (y1 == y && x1 <= x && x1 + dir[1] >= x) return false;
			x1 += dir[1];
		}
		if (ds[i] == 2) {
			if (y1 == y && x1 >= x && x1 - dir[2] <= x) return false;
			x1 -= dir[2];
		}
		if (ds[i] == 3) {
			if (x1 == x && y1 <= y && y1 + dir[3] >= y) return false;
			y1 += dir[3];
		}
		if (ds[i] == 4) {
			if (x1 == x && y1 >= y && y1 - dir[4] <= y) return false;
			y1 -= dir[4];
		}
	}
	return true;
}

void solve() {
	flag = 0;
	cin >> x >> y;
	cin >> s;
	dir[1] = count(s.begin(), s.end(), 'R');
	dir[2] = count(s.begin(), s.end(), 'L');
	dir[3] = count(s.begin(), s.end(), 'U');
	dir[4] = count(s.begin(), s.end(), 'D');
	
	do {
		if (check()) {
			flag = 1;
			for (int i = 0; i <= 3; i++) {
				for (int j = 0; j < dir[ds[i]]; j++)
					cout << dp[ds[i]];
			}
			break;
		}
	} while (next_permutation(ds, ds + 4));
		
		if (!flag)
			cout << "Impossible";
		cout << endl;
}


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