#include<bits/stdc++.h>
using namespace std;
#define int long long
string ss;
void solve(){
	int xd,yd;
	cin >> xd >> yd;
	cin >> ss;
	//cout << ss << "\n";
	int len=ss.size();
	int u=0,d=0,l=0,r=0;
	for(int i=0; i<len; i++){
		if(ss[i]=='R') r++;
		if(ss[i]=='U') u++;
		if(ss[i]=='L') l++;
		if(ss[i]=='D') d++;
	}
	if(r-l==xd && u-d==yd){
		cout << "Impossible\n";
		return;
	}
	if(xd==0 && yd==0){
		cout << "Impossible\n";
		return;
	}
	if(xd!=0 && yd!=0){
		int mbx=r-l;
		if(mbx==xd){
			while(u!=0){
				u--;
				cout << "U";
			}
			while(d!=0){
				d--;
				cout << "D";
			}
			while(l!=0){
				l--;
				cout << "L";
			}
			while(r!=0){
				r--;
				cout << "R";
			}
		}
		else{
			while(l!=0){
				l--;
				cout << "L";
			}
			while(r!=0){
				r--;
				cout << "R";
			}
			while(u!=0){
				u--;
				cout << "U";
			}
			while(d!=0){
				d--;
				cout << "D";
			}
		}
	}
	if(xd!=0 && yd==0){
		if(u==0 && d==0){
			if(xd>0){
				if(r-l>=xd){
					cout << "Impossible\n";
					return;
				}
				else{
					while(l!=0){
						l--;
						cout << "L";
					}
					while(r!=0){
						r--;
						cout << "R";
					}
				}
			}
			else{
				if(l-r>=-1*xd){
					cout << "Impossible\n";
					return;
				}
				else{
					while(r!=0){
						r--;
						cout << "R";
					}
					while(l!=0){
						l--;
						cout << "L";
					}
				}
			}
		}
		else{
			if(u!=0){
				while(u!=0){
					u--;
					cout << "U";
				}
				while(r!=0){
					r--;
					cout << "R";
				}
				while(l!=0){
					l--;
					cout << "L";
				}
				while(d!=0){
					d--;
					cout << "D";
				}
			}
			else{
				while(d!=0){
					d--;
					cout << "D";
				}
				while(r!=0){
					r--;
					cout << "R";
				}
				while(l!=0){
					l--;
					cout << "L";
				}
				while(u!=0){
					u--;
					cout << "U";
				}
			}
		}
	}
	if(xd==0 && yd!=0){
		if(l==0 && r==0){
			if(yd>0){
				if(u-d>=yd){
					cout << "Impossible\n";
					return;
				}
				else{
					while(d!=0){
						d--;
						cout << "D";
					}
					while(u!=0){
						u--;
						cout << "U";
					}
				}
			}
			else{
				if(d-u>=-1*yd){
					cout << "Impossible\n";
					return;
				}
				else{
					while(u!=0){
						u--;
						cout << "U";
					}
					while(d!=0){
						d--;
						cout << "D";
					}
				}
			}
		}
		else{
			if(r!=0){
				while(r!=0){
					r--;
					cout << "R";
				}
				while(u!=0){
					u--;
					cout << "U";
				}
				while(d!=0){
					d--;
					cout << "D";
				}
				while(l!=0){
					l--;
					cout << "L";
				}
			}
			else{
				while(l!=0){
					l--;
					cout << "L";
				}
				while(u!=0){
					u--;
					cout << "U";
				}
				while(d!=0){
					d--;
					cout << "D";
				}
				while(r!=0){
					r--;
					cout << "R";
				}
			}
		}
	}
	cout << "\n";
	return;
}
signed main(){
	ios::sync_with_stdio(false),cin.tie(0);
	int _=1;
	cin>>_;
	while(_--) solve();
}