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

int a[6];

void solve()
{
	int x, y, u, d, l, r;
	u = d = l = r = 0;
	string s;
	//memset(a,0,sizeof a);
	for (int i = 1; i <= 4; i++) {
		a[i] = i;
	}
	bool f = false;
	int ax = 0, ay = 0;
	cin >> x >> y;
	if (x == 0 && y == 0) {
		cout << "Impossible" << endl;
		return;
	}
	cin >> s;
	for (int i = 0; i < s.size(); i++) {
		if (s[i] == 'U') {
			u++;
			ax++;
		}
		if (s[i] == 'D') {
			d++;
			ax--;
		}
		if (s[i] == 'R') {
			r++;
			ay++;
		}
		if (s[i] == 'L') {
			l++;
			ay--;
		}
	}
	if (ay == x &&ay == y) {
		cout << "Impossible" << endl;
		return;
	}
	while (true) {
		int xx = 0, yy = 0;
		bool flag = true;
		for (int i = 1; i <= 4; i++) {
			if (a[i] == 1 && xx == x && y >= yy && y <= yy + u) {
				flag = false;
				break;
			}
			if (a[i] == 2 && xx == x && y >= yy - d && y <= yy) {
				flag = false;
				break;
			}
			if (a[i] == 3 && yy == y && x >= xx - l && x <= xx) {
				flag = false;
				break;
			}
			if (a[i] == 4 && yy == y && y <= xx + r && x >= xx) {
				flag = false;
				break;
			}
			if (a[i] == 1) {
				yy += u;
			}
			else if (a[i] == 2) {
				yy -= d;
			}
			else if (a[i] == 3) {
				xx -= l;
			}
			else if (a[i] == 4) {
				xx += r;
			}
		}
		if (flag) {
			for (int i = 1; i <= 4; i++) {
				if (a[i] == 1) {
					for (int j = 1; j <= u; j++) {
						cout << "U";
					}
				}
				if (a[i] == 2) {
					for (int j = 1; j <= d; j++) {
						cout << "D";
					}
				}
				if (a[i] == 3) {
					for (int j = 1; j <= l; j++) {
						cout << "L";
					}
				}
				if (a[i] == 4) {
					for (int j = 1; j <= r; j++) {
						cout << "R";
					}
				}
			}
			cout << endl;
			f = true;
			break;
		}
		if (!next_permutation(a + 1, a + 5)) {
			break;
		}
	}
	if (!f) {
		cout << "Impossible" << endl;
		return;
	}
	return;

}


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

	int T = 1;
	cin >> T;
	while (T--)
	{
		solve();
	}
	return 0;
}