#include <bits/stdc++.h>
#define int long long
using namespace std;
vector<char> ans;
int end_x,end_y;
unordered_map<char,int> mp;
int f=0;
int mx,my;
void dfs(int nowx,int nowy){
	if(nowx==end_x&&nowy==end_y){
		f=1;
		return;
	}
			if(nowx+1!=mx&&nowy!=my&&mp['R']){
				mp['R']--;
				ans.emplace_back('R');
				dfs(nowx+1,nowy);
				mp['R']++;ans.pop_back();
				if(f)return;
			}
			if(nowx-1!=mx&&nowy!=my&&mp['L']){
				mp['L']--;
				ans.emplace_back('L');
				dfs(nowx-1,nowy);
				mp['L']++;ans.pop_back();
				if(f)return;
			}
			if(nowx!=mx&&nowy+1!=my&&mp['U']){
				mp['U']--;
				ans.emplace_back('U');
				dfs(nowx,nowy+1);
				mp['U']++;ans.pop_back();
				if(f)return;	
			}
			if(nowx!=mx&&nowy-1!=my&&mp['D']){
				mp['D']--;
				ans.emplace_back('D');
				dfs(nowx,nowy-1);
				mp['D']++;ans.pop_back();
				if(f)return;	
			}

}
void solve() {
	cin>>mx>>my;
	string str;
	cin>>str;
	f=0;ans.clear();
	if(mx==0&&my==0) {
		cout<<"Impossible"<<endl;
		return;
	}
	mp.clear();
	for(int i=0; i<str.length(); i++) {
		mp[str[i]]++;//统计各个方向移动的指令数目
	}
	end_x=mp['R']-mp['L'];//不要取绝对值就是算最后的坐标
	end_y=mp['U']-mp['D'];
	if(mx==end_x&&my==end_y){
		cout<<"Impossible"<<endl;
		return;
	}
	if(end_x!=mx&&end_y!=my) { //如果两个最终的结果都不跟坐标相同
		dfs(0,0);
		for(auto it:ans)cout<<it;
		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=1;i<=min(mp['L'],mp['R']); i++) {
				cout<<'L'<<'R';
			}
			for(int i=min(mp['L'],mp['R'])+1; i<=max(mp['L'],mp['R']); i++) {
				if(mp['L']>mp['R'])
					cout<<'L';
				else 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=1; i<=min(mp['U'],mp['D']); i++) {
				cout<<'U'<<'D';
			}
			for(int i=min(mp['U'],mp['D'])+1;i<=max(mp['U'],mp['D']); i++){
				if(mp['U']>mp['D'])
					cout<<'U';
				else 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();
	}
}