#include<iostream>
#include<algorithm>
#include<cmath>
using namespace std;
#define int long long

int cnt[4];

void solve()
{
	fill(cnt, cnt + 4, 0);
	int xx, yy;
	string s;
	cin >> xx >> yy >> s;
	if (xx == 0 && yy == 0)
	{
		cout << "Impossible" << endl;
		return;
	}
	for (int i = 0; i < s.length(); i++)
	{
		if (s[i] == 'U')
		{
			cnt[0]++;
		}
		else if (s[i] == 'D')
		{
			cnt[1]++;
		}
		else if (s[i] == 'L')
		{
			cnt[2]++;
		}
		else 
		{
			cnt[3]++;
		}
	}
	if (xx == abs(cnt[3] - cnt[2]) && yy == abs(cnt[0] - cnt[1]))
	{
		cout << "Impossible" << endl;
		return;
	}
	string t = "UDLR";
	int x, y, f;
	do
	{
		f = 1;
		x = 0, y = 0;
		for (auto i : t)
		{
			switch (i)
			{
			case 'U':
				for (int j = 0; j < cnt[0]; j++)
				{
					y++;
					if (x == xx && y == yy)
					{
						f = 0;
						break;
					}
				}
				break;
			case 'D':
				for (int j = 0; j < cnt[1]; j++)
				{
					y--;
					if (x == xx && y == yy)
					{
						f = 0;
						break;
					}
				}
				break;
			case 'L':
				for (int j = 0; j < cnt[2]; j++)
				{
					x--;
					if (x == xx && y == yy)
					{
						f = 0;
						break;
					}
				}
				break;
			case 'R':
				for (int j = 0; j < cnt[3]; j++)
				{
					x++;
					if (x == xx && y == yy)
					{
						f = 0;
						break;
					}
				}
				break;
			default:
				break;
			}
		}
		if (!f)
		{
			break;
		}
	} while (!f && next_permutation(t.begin(), t.end()));//四个方向全排列
	if (f)
	{
		for (auto i : t)
		{
			switch (i)
			{
			case 'U':
				for (int j = 0; j < cnt[0]; j++)
				{
					cout << 'U';
				}
				break;
			case 'D':
				for (int j = 0; j < cnt[1]; j++)
				{
					cout << 'D';
				}
				break;
			case 'L':
				for (int j = 0; j < cnt[2]; j++)
				{
					cout << 'L';
				}
				break;
			case 'R':
				for (int j = 0; j < cnt[3]; j++)
				{
					cout << 'R';
				}
				break;
			default:
				break;
			}
		}
		cout << endl;
	}
	else
	{
		cout << "Impossible" << endl;
	}
}

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

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