#include <bits/stdc++.h>
using namespace std;
const int MAXSIZE=200005;
long long even[MAXSIZE],odd[MAXSIZE];
void solve() {
	int mx,my;
	cin>>mx>>my;
	string str;
	cin>>str;
	if(mx==0&&my==0) {
		cout<<"Impossible"<<endl;
		return;
	}
	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
		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_x!=mx&&end_y==my) {//若x不相同,但是y的坐标相同的话
		if(end_x>0&&end_x>mx) {
			cout<<"Impossible"<<endl;
			return;
		} else if(end_x<0&&end_x<mx) {
			cout<<"Impossible"<<endl;
			return;
		} else {
			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(end_y>0&&end_y>my) {
			cout<<"Impossible"<<endl;
			return;
		} else if(end_y<0&&end_y<my) {
			cout<<"Impossible"<<endl;
			return;
		} else {
			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;
		}
	} 
	
	else {
		cout<<"Impossible"<<endl;
		return;
	}


}
int main() {
	int t;
	cin>>t;
	while(t--) {
		solve();
	}
}