#include<bits/stdc++.h>
using namespace std;
// #define int short
#define int long long

typedef long long ll;

int f = 0;

map<int , char> ump , uump;

void solve()
{
    int x , y;
    cin >> x >> y;
    map<int , int> mp;
    ump[1] = 'U';
    ump[2] = 'D';
    ump[3] = 'L';
    ump[4] = 'R';
    uump['U'] = 1;
    uump['D'] = 2;
    uump['L'] = 3;
    uump['R'] = 4;


    string s;
    cin >> s;
    

    for(int i = 0; s[i]; i ++)
    {
        mp[uump[s[i]]] ++;
    }

    vector<int> v;
    for(int i = 1; i <= 4; i ++)
    {
        v.push_back(i);
    }

    int xx = 0 , yy = 0;
    
    if(!x && !y)
    {
        cout << "Impossible\n";
        return ;
    }

    int cnt = 0;
    do
    {
        // ++ cnt;
        xx = 0 , yy = 0 , f = 0;
        for(int i = 0; i < v.size(); i ++)
        {
            if(v[i] == 1)
            {
                yy += mp[v[i]];
                if(xx == x && ((abs(yy) >= abs(y) && ((yy >= 0 && y >= 0) || (yy < 0 && y < 0))) || yy == y))
                {
                    f = 1;
                    continue ;
                }
            }
            else if(v[i] == 2)
            {
                yy -= mp[v[i]];
                if(xx == x && ((abs(yy) >= abs(y) && ((yy >= 0 && y >= 0) || (yy < 0 && y < 0))) || yy == y))
                {
                    f = 1;
                    continue ;
                }
            }
            else if(v[i] == 3)
            {
                xx -= mp[v[i]];
                if(yy == y && ((abs(xx) >= abs(x) && ((xx >= 0 && x >= 0) || (xx < 0 && x < 0))) || xx == x))
                {
                    f = 1;
                    continue ;
                }
            }
            else
            {
                xx += mp[v[i]];
                // if(cnt == 9)
                // {
                //     cout << x << ' ' << y << '\n';
                //     cout << xx << ' ' << yy << '\n';

                // }
                if(yy == y && ((abs(xx) >= abs(x) && ((xx >= 0 && x >= 0) || (xx < 0 && x < 0))) || xx == x))
                {
                    f = 1;
                    continue ;
                }
            }
        }
        if(f) continue ;
        for(int i = 0; i < v.size(); i ++)
        {
            for(int j = 1; j <= mp[v[i]]; j ++)
            {
                cout << ump[v[i]];
            }
        }
        
        cout << '\n';
        // cout << cnt << '\n';
        return ;
    }
    while(next_permutation(v.begin(),v.end())); 
    

    cout << "Impossible\n";



}



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

    int _ = 1;
    cin >> _;
    while(_ --)
    {
        solve();
    }

    // for(int i = 1; i <= _; i ++)
    // {
    //     f = 0;
    //     if(i == 28) f = 1;
    //     else solve();
    // }

    return 0;
}