#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<map>
#include<iomanip>
#include<cmath>
using namespace std;
using ll = long long;
#define int ll

void solve()
{
	int xx, yy;
	cin >> xx >> yy;
	string s;
	cin >> s;
	if (xx == 0 && yy == 0)
	{
		cout << "Impossible" << endl;
		return;
	}
    int u = 0, r = 0, l = 0, d = 0;
    for (int i = 0; i < s.length(); i++)
    {
        switch (s[i])
        {
        case 'U':
            u++;
            break;
        case 'D':
            d++;
            break;
        case 'R':
            r++;
            break;
        case 'L':
            l++;
            break;
        default:
            break;
        }
    }
    if (xx == abs(r - l) && yy == abs(u - d))
    {
        cout << "Impossible" << endl;
        return;
    }
    bool f = 1;
    do
    {
        f = 1;
        int x = 0, y = 0;
        for (int i = 0; i < s.length(); i++)
        {
            switch (s[i])
            {
            case 'U':
                y++;
                break;
            case 'D':
                y--;
                break;
            case 'R':
                x++;
                break;
            case 'L':
                x--;
                break;
            default:
                break;
            }
            if (x == xx && y == yy)
            {
                f = 0;
                break;;
            }
        }
    } while (!f && next_permutation(s.begin(), s.end()));
    if (!f)
    {
        cout << "Impossible" << endl;
    }
    else
    {
        cout << s << endl;
    }
}

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

	int T;
	cin >> T;
	while (T--)
	{
		solve();
	}

	return 0;
}