#include<algorithm>
#include<iostream>
#include<cstring>
#include<string>
#include<map>

using namespace std;
int mx, my;
int a[4] = { 0,1,2,3 };//U D L R
int cnt[4] = { 0 };
int op[4][2] = { {0,1},{0,-1},{-1,0},{1,0} };
bool check() {
	int x = 0, y = 0;
	for (int i = 0; i < 4; i++)
	{
		for (int j = 0; j < cnt[a[i]]; j++)
		{
			x += op[a[i]][0];
			y += op[a[i]][1];
			if (x == mx && y == my)  return false;
		}
	}
	return true;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);

	int t;
	cin >> t;
	map<int, string>mp;
	mp[0] = 'U', mp[1] = 'D', mp[2] = 'L', mp[3] = 'R';
	while (t--) 
	{
		cin >> mx >> my;
		string s;
		cin >> s;
		int x = 0, y = 0;
		memset(cnt, 0, sizeof(cnt));
		a[0] = 0, a[1] = 1, a[2] = 2, a[3] = 3;
		for (int i = 0; i < s.size(); i++) 
		{
			if (s[i] == 'U')
			{
				cnt[0]++;
			}
			if (s[i] == 'D')
			{
				cnt[1]++;
			}
			if (s[i] == 'L')
			{
				cnt[2]++;
			}
			if (s[i] == 'R')
			{
				cnt[3]++;
			}
		}
		if ((mx == 0 && my == 0) || (x == abs(cnt[2] - cnt[3]) && y == abs(cnt[0] - cnt[1])))
		{
			cout << "Impossible\n";
			continue;
		}
		bool ok = false;
			do {
				if (check())
				{
					ok = true;
					for (int i = 0; i < 4; i++)
					{
						for (int j = 0; j < cnt[a[i]]; j++)
							cout << mp[a[i]];
					}
					cout << endl;
					break;
				}
			} while (next_permutation(a, a + 4));
		if (!ok)
		{
			cout << "Impossible\n";
		}
	}

	return 0;
}