#include<bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int, int> PII;
int dx[4] = {0, 1, 0, -1};
int dy[4] = {1, 0, -1, 0};
int x, y;
map <char, int> mt;
bool is;
map <char, int> l;
bool check(char t[])
{
    int tx = 0, ty = 0;
    for(int i = 0; i < 4; i ++ )
    {
        for(int j = 0; j < l[t[i]]; j ++ )
        {
            tx += dx[mt[t[i]]];
            ty += dy[mt[t[i]]];
            if(tx == x && ty == y)
            {
                return false;
            }
        }
    }
    return true;
}
void solve() 
{
    l.clear();
    std:: cin >> x >> y;
    string s;
    std:: cin >> s;
    if(x == 0 && y == 0)
    {
        std:: cout << "Impossible" << endl;
        return ;
    }

    int m = 0, n = 0;
    for(int i = 0; i < s.length(); i ++ )
    {   
        m += dx[mt[s[i]]];
        n += dy[mt[s[i]]];
    }

    if(m == x && n == y)
    {
        std:: cout << "Impossible" << endl;
        return ;        
    }

    for(int i = 0; i < s.length(); i ++ )
    {
        l[s[i]] ++ ;
    }

    vector <char> ans;
    char t[4] = {'D', 'L', 'R', 'U'};
    do
    {
        // for(int i = 0; i < 4; i ++ )
        // {
        //     std:: cout << t[i] << " ";
        // }
        is = true;
        if(check(t))
        {
            is = false;
            for(int i = 0; i < 4; i ++ )
            {
                for(int j = 0; j < l[t[i]]; j ++ )
                {
                    ans.push_back(t[i]);
                }
            }
        }
        if(!is)
        {
            break;
        }
    } while (next_permutation(t, t + 4));
    
    if(is)
    {
        std:: cout << "Impossible" << endl;
        return ;   
    }
    else
    {
        for(auto p : ans)
        {
            std:: cout << p;
        }
    }
    std:: cout << endl;
}

signed main()
{
	ios::sync_with_stdio(false);
	cin.tie(0), cout.tie(0);
    mt['U'] = 0;
    mt['L'] = 3;
    mt['R'] = 1;
    mt['D'] = 2;
    int T;
    std:: cin >> T;
    while(T -- )
	solve();
	return 0;
}