#include <iostream>
#include <cstring>
#include <map>
using namespace std;
void solve()
{
	int x,y;cin>>x>>y;
	string s;cin>>s;
	map<char,int> mp;
	int edx=0,edy=0;
	for(int i=0;i<s.size();i++) {
		mp[s[i]]++;
		if(s[i]=='R') {
			edx++;
		}
		else if(s[i]=='L') {
			edx--;
		}
		else if(s[i]=='U') {
			edy++;
		}
		else {
			edy--;
		}
	}
	if(edx==x&&edy==y||x==0&&y==0) {
		cout<<"Impossible"<<endl;
		return ;
	} 
	int sum1=mp['R'],sum2=mp['L'],sum3=mp['U'],sum4=mp['D'];
	if(sum3>=y&&sum1==0&&sum2==0&&sum4==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if(sum1>=x&&sum3==0&&sum2==0&&sum4==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if(sum4>=abs(y)&&y<=0&&sum1==0&&sum2==0&&sum3==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if(sum2>=abs(x)&&x<=0&&sum1==0&&sum3==0&&sum4==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if(x>=0&&y>=0) {
		while(sum2--) cout<<'L';
		while(sum4--) cout<<'D';
		while(sum1--) cout<<'R';
		while(sum3--) cout<<'U';
		cout<<endl;
	}
	else if(x>=0&&y<0) {
		while(sum2--) cout<<'L';
		while(sum3--) cout<<'U';
		while(sum1--) cout<<'R';
		while(sum4--) cout<<'D';
		cout<<endl;
	}
	else if(x<0&&y>=0) {
		while(sum1--) cout<<'R';
		while(sum4--) cout<<'D';
		while(sum3--) cout<<'U';
		while(sum2--) cout<<'L';
		cout<<endl;
	}
	else if(x<0&&y<0) {	
		while(sum1--) cout<<'R';
		while(sum3--) cout<<'U';
		while(sum2--) cout<<'L';
		while(sum4--) cout<<'D';
		cout<<endl;
	}
}
int main()
{
	int t;
	cin>>t;
	while(t--){
		solve();
	}
	return 0;
}