//
// Created by travel on 2024/10/11.
//
#include<bits/stdc++.h>
using namespace std;
#define int long long
typedef pair<int,int> PII;
#define endl "\n"
#define ft first
#define sd second
#define pb push_back
const int mod = 1e9 + 7;
int mx,my;
char st[5] = {'L','R','U','D'};
map<char,int> mp;
vector<char> v;
bool check(int mx,int my){
    int x = 0,y = 0;
    for(int i = 0;i < 4;i++){
        for(int j = 1;j <= mp[v[i]];j++)
        {
            if(v[i] == 'L') x--;
            if(v[i] == 'R') x++;
            if(v[i] == 'D') y--;
            if(v[i] == 'U') y++;
            if(x == mx && y == my ) return false;
        }
    }
    return true;
}
void solve(){
    cin>>mx>>my;
    string s; cin>>s;
    string ed = "Impossible";
    if(mx == 0 && my == 0){
        cout<<ed<<endl;
        return ;
    }
    int x = 0,y = 0;
    mp.clear();
    for(int i = 0;i < s.size();i++){
        if(s[i] == 'R') x++;
        if(s[i] == 'L') x--;
        if(s[i] == 'U') y++;
        if(s[i] == 'D') y--;
        mp[s[i]]++;
    }
    v.clear();
    for(int i = 0;i < 4;i++)
        v.pb(st[i]);
    if(x == mx && y == my){
        cout<<ed<<endl;
        return ;
    }
    if(mp.size() == 1){
        if(x == 0 && abs(y) > abs(my))
        {
            cout<<ed<<endl;
            return ;
        }
        if(y == 0 && abs(x) > abs(mx))
        {
            cout<<ed<<endl;
            return ;
        }
        cout<<s<<endl;
        return ;
    }
    for(int i = 1;i <= 24;i++){
        next_permutation(v.begin(),v.end());
        if(check(mx,my))
        {
            for(int j = 0;j < v.size();j++)
                while(mp[v[j]] >= 1)
                {
                    cout<<v[j];
                    mp[v[j]]--;
                }
            break;
        }
    }
    cout<<endl;
    return ;
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int T ; cin>>T;
    while(T--)
        solve();
    return 0;
}
/*
 * 5
1 1
RURULLD
0 5
UUU
0 3
UUU
0 2
UUU
0 0
UUU
 */