#include <bits/stdc++.h>
#define int long long
using namespace std;
void solve() {
int mx,my;
cin>>mx>>my;
string str;
cin>>str;
if(mx==0&&my==0) {
cout<<"Impossible"<<endl;
return;
}
if(mx==end_x&&my==end_y){
cout<<"Impossible"<<endl;
return;
}
unordered_map<char,int> mp;
for(int i=0; i<str.length(); i++) {
mp[str[i]]++;//统计各个方向移动的指令数目
}
int end_x=mp['R']-mp['L'];//不要取绝对值就是算最后的坐标
int end_y=mp['U']-mp['D'];
if(end_x!=mx&&end_y!=my) { //如果两个最终的结果都不跟坐标相同
int nowx=0,nowy=0;
while(mp['L']+mp['R']+mp['U']+mp['D']){
if(nowx+1!=mx&&nowy!=my&&mp['R']){
mp['R']--;nowx++;
cout<<'R';
}
else if(nowx-1!=mx&&nowy!=my&&mp['L']){
mp['L']--;nowx--;
cout<<'L';
}
else if(nowx!=mx&&nowy+1!=my&&mp['U']){
mp['U']--;nowy++;
cout<<'U';
}
else if(nowx!=mx&&nowy-1!=my&&mp['D']){
mp['D']--;nowy--;
cout<<'D';
}
}
cout<<endl;
return;
}
else if(end_x!=mx&&end_y==my) {//若x不相同,但是y的坐标相同的话
if(mx>0&&end_x>mx){
cout<<"Impossible"<<endl;
return;
}
else if(mx<0&&end_x<mx){
cout<<"Impossible"<<endl;
return;
}
for(int i=0; i<mp['L']; i++) {
cout<<'L';
}
for(int i=0; i<mp['R']; i++) {
cout<<'R';
}
for(int i=0; i<mp['U']; i++) {
cout<<'U';
}
for(int i=0; i<mp['D']; i++) {
cout<<'D';
}
cout<<endl;
return;
}
else if(end_y!=my&&end_x==mx) { //如果y最后不相同但是x相同,
if(my>0&&end_y>my){
cout<<"Impossible"<<endl;
return;
}
else if(my<0&&end_y<my){
cout<<"Impossible"<<endl;
return;
}
for(int i=0; i<mp['U']; i++) {
cout<<'U';
}
for(int i=0; i<mp['D']; i++) {
cout<<'D';
}
for(int i=0; i<mp['L']; i++) {
cout<<'L';
}
for(int i=0; i<mp['R']; i++) {
cout<<'R';
}
cout<<endl;
return;
}
}
signed main() {
ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
int t;
cin>>t;
while(t--) {
solve();
}
}