#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;
void solve() 
{
    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 ;        
    }

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

    if(l[s[0]] == s.length())
    {
        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 && l[s[0]] == s.length())
            {
                std:: cout << "Impossible" << endl;
                return ;                
            }
        }        
    }
    int tx = 0, ty = 0;
    if(x != m)
    {
        for(int i = 0; i < l['L']; i ++ )
        {
            std:: cout << 'L';
        }
        for(int j = 0; j < l['R']; j ++ )
        {
            std:: cout << 'R';
        }       
        for(int i = 0; i < l['U']; i ++ )
        {
            std:: cout << "U";
        }           
        for(int i = 0; i < l['D']; i ++ )
        {
            std:: cout << 'D';
        }
        std:: cout << endl;        
    }
    else if(y != n)
    {
        for(int i = 0; i < l['D']; i ++ )
        {
            std:: cout << 'D';
        }
        for(int i = 0; i < l['U']; i ++ )
        {
            std:: cout << "U";
        }
        for(int j = 0; j < l['R']; j ++ )
        {
            std:: cout << 'R';
        }         
        for(int i = 0; i < l['L']; i ++ )
        {
            std:: cout << 'L';
        }
        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;
}