#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;

const int N = 1e5 + 10;
#define int long long
int n, m;
int mx = 0;
int ans = 0;
int l, r, u, d;

void solve()
{
    int mx, my;
    cin >> mx >> my;
    l = r = u = d = 0;
    string s;
    cin >> s;
    for (int i = 0; i < s.size(); i++)
    {
        if (s[i] == 'L')l++;
        else if (s[i] == 'R')r++;
        else if (s[i] == 'U')u++;
        else d++;
    }

    if (mx == 0 && my == 0)
    {
        cout << "Impossible" << endl;
        return;
    }
    if (mx == 0)
    {
        if (l == 0 && r == 0&&((my<0&&u-d<=my)||(my>0&&u-d>=my))) {
            cout << "Impossible" << endl;
            return;
        }
    }
    if (my == 0)
    {
        if (u == 0 && d == 0&&((mx<0&&r-l<=mx)||(mx>0&&r-l>=mx)))
        {
            cout << "Impossible" << endl;
            return;
        }
    }

    if (((mx<0&&mx==r-l)&&(my<0&&my==u-d))|| ((mx > 0 && mx == r - l) && (my < 0 && my == u - d))|| ((mx < 0 && mx == r - l) && (my > 0 && my == u - d))|| ((mx > 0 && mx == r - l) && (my > 0 && my == u - d))) {
        cout << "Impossible" << endl;
        return;
    }
    
    if (mx==0)
    {
        if (l != 0) {
            cout << "L";
            l--;
        }
        else if (r != 0)
        {
            cout << "R";
            r--;
        }
        if (my < 0)
        {
            while (u)
            {
                cout << "U";
                u--;
            }
            while (d)
            {
                cout << "D";
                d--;
            }
        }
        else {
            while (d)
            {
                cout << "D";
                d--;
            }
            while (u)
            {
                cout << "U";
                u--;
            }
            
        }
        while (l) {
            cout << "L";
            l--;
        }
        while (r)
        {
            cout << "R";
            r--;
        }
        cout << endl;
        return;
    }

    if (my == 0)
    {
        if (u != 0)
        {
            cout << "U";
            u--;
        }
        else if (d != 0)
        {
            cout << "D";
            d--;
        }
        if (mx < 0)
        {while (r)
            {
                cout << "R";
                r--;
            }
            while (l) {
                cout << "L";
                l--;
            }
            
        }
        else {
            while (l) {
                cout << "L";
                l--;
            }
            while (r)
            {
                cout << "R";
                r--;
            }
        }
        while (u)
        {
            cout << "U";
            u--;
        }
        while (d)
        {
            cout << "D";
            d--;
        }
        cout << endl;
        return;
    }

    while (l) {
        cout << "L";
        l--;
    }
    while (r)
    {
        cout << "R";
        r--;
    }
    while (u)
    {
        cout << "U";
        u--;
    }
    while (d)
    {
        cout << "D";
        d--;
    }
    cout << endl;
}

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