//
// 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;
void solve(){
    cin>>mx>>my;
    string s; cin>>s;
    if(mx == 0 && my == 0){
        cout<<"Impossible"<<endl;
        return ;
    }
    int x = 0,y = 0;
    map<char,int> mp;
    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]]++;
    }
    if(x == mx && y == my){
        cout<<"Impossible"<<endl;
        return ;
    }
    x = 0,y = 0;
    int cnt = 0;
    vector<char> v;
    while(cnt < s.size()){
        bool flag = 0;
        if(mp['L'] >= 1 && ((x - 1 != mx || y != my))){
                mp['L']--;
                x--;
                v.pb('L');
                flag = 1;
                cnt++;
        }
        else if(mp['R'] >= 1 && ((x + 1 != mx || y != my))){
            mp['R']--;
            x ++;
            v.pb('R');
            flag = 1;
            cnt++;
        }
        else if(mp['U'] >= 1 && (y + 1 != my || x != mx))
        {
            mp['U']--;
            y++;
            v.pb('U');
            flag = 1;
            cnt++;
        }
        else if(mp['D'] >= 1 && (y - 1 != my || x != mx)){
            mp['D']--;
            y--;
            v.pb('D');
            flag = 1;
            cnt++;
        }
//        cout<<cnt<<' '<<flag<<endl;
        if(flag == 0)
            break;
    }
    if(cnt < s.size())
    {
        cout<<"Impossible"<<endl;
        return ;
    }
    for(auto it : v)
        cout<<it;
    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
 */