#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]++;  y++;
			}
			if (s[i] == 'D') 
			{
				cnt[1]++; y--;
			}
			if (s[i] == 'L') 
			{
				cnt[2]++; x--;
			}
			if (s[i] == 'R') 
			{
				cnt[3]++;  x++;
			}
		}
		if ((mx == 0 && my == 0) || (x == mx && y == my))
		{
			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;
}