#include <iostream>
#include <cstring>
#include <map>
using namespace std;
char op[4]={'L','R','U','D'};
void solve()
{
	int x,y;cin>>x>>y;
	string s;cin>>s;
	string ans;
	int len=s.size();
	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-sum4)>=y&&y>=0&&x==0&&sum1==0&&sum2==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if((sum1-sum2)>=x&&x>=0&&y==0&&sum3==0&&sum4==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if((sum4-sum3)>=abs(y)&&y<=0&&x==0&&sum1==0&&sum2==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	if((sum2-sum1)>=abs(x)&&x<=0&&y==0&&sum3==0&&sum4==0) {
		cout<<"Impossible"<<endl;
		return ;
	}
	int ex=0,ey=0;
	for(int i=0;i<len;i++) {
		for(int j=0;j<4;j++) {
			int tx=ex,ty=ey;
			bool f=0;
			if(op[j]=='L'&&mp['L']>0) tx=ex-1,f=1;
			if(op[j]=='R'&&mp['R']>0) tx=ex+1,f=1;
			if(op[j]=='U'&&mp['U']>0) ty=ey+1,f=1;
			if(op[j]=='D'&&mp['D']>0) ty=ey-1,f=1;
			if(f&&(tx!=x||ty!=y)) {
			mp[op[j]]--;
			ex=tx,ey=ty;
			cout<<op[j];
			break;
			}
		}
	}
	cout<<endl;
}
int main()
{
	int t;
	cin>>t;
	while(t--){
		solve();
	}
	return 0;
}