#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;
void pd(int tx, int ty)
{
    if(tx == x && ty == y)
    {
        is = false;
        return ;
    }
}
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 ;                
            }
        }        
    }
    is = true;
    int tx = 0, ty = 0;
    vector <char> ans;
    if(x != m)
    {
        for(int i = 0; i < l['L']; i ++ )
        {
            tx += dx[mt['L']];
            ty += dy[mt['L']];
            pd(tx, ty);
            ans.push_back('L');
        }
        for(int i = 0; i < l['R']; i ++ )
        {
            tx += dx[mt['R']];
            ty += dy[mt['R']];
            pd(tx, ty);
            ans.push_back('R');
        }       
        for(int i = 0; i < l['U']; i ++ )
        {
            tx += dx[mt['U']];
            ty += dy[mt['U']];
            pd(tx, ty);
            ans.push_back('U');
        }           
        for(int i = 0; i < l['D']; i ++ )
        {
            tx += dx[mt['D']];
            ty += dy[mt['D']];
            pd(tx, ty);
            ans.push_back('D');
        }     
    }
    else if(y != n)
    {
        for(int i = 0; i < l['U']; i ++ )
        {
            tx += dx[mt['U']];
            ty += dy[mt['U']];
            pd(tx, ty);
            ans.push_back('U');
        }           
        for(int i = 0; i < l['D']; i ++ )
        {
            tx += dx[mt['D']];
            ty += dy[mt['D']];
            pd(tx, ty);
            ans.push_back('D');
        }
        for(int i = 0; i < l['L']; i ++ )
        {
            tx += dx[mt['L']];
            ty += dy[mt['L']];
            pd(tx, ty);
            ans.push_back('L');
        }
        for(int i = 0; i < l['R']; i ++ )
        {
            tx += dx[mt['R']];
            ty += dy[mt['R']];
            pd(tx, ty);
            ans.push_back('R');
        }  
    }

    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;
}