#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>
#include<vector>
#include<stack>
#define int long long
//#define endl '\n'
using namespace std;
typedef pair<int,int> PII;
const int N=200200;
int n;
int a[N],b[N];
int x,y;
string s;
int o=0,p=0;
map<char,int> m;
void solve(){
	m.clear();
	cin>>x>>y>>s;
	string ans;
	ans.clear();
	if(x==0&&y==0){
		cout<<"Impossible"<<endl;
		return;
	}
	for(int i=0;i<s.size();i++){
		if(s[i]=='L') o--;
		if(s[i]=='R') o++;
		if(s[i]=='U') p++;
		if(s[i]=='D') p--;
		m[s[i]]++;
	}
	if(o==x&&p==y){
		cout<<"Impossible"<<endl;
		return;
	}
	//cout<<"11"<<endl;
	if(x!=0&&y!=0){
		//cout<<o<<p<<endl;
		if(x>=0){
			while(m['L']){
				ans+='L';
				m['L']--;
			}
		}
		else{
			while(m['R']){
				ans+='R';
				m['R']--;
			}
		}
		if(y>=0){
			while(m['U']){
				ans+='U';
				m['U']--;
			}
		}
		else{
			while(m['D']){
				ans+='D';
				m['D']--;
			}
		}
		while(m['L']) ans+='L',m['L']--;
		while(m['R']) ans+='R',m['R']--;
		while(m['U']) ans+='U',m['U']--;
		while(m['D']) ans+='D',m['D']--;
		cout<<ans<<endl;
		return;
	}
	if(x==0){
		int yy=0;
		bool st=0;
		if(m['L']) ans+='L',m['L']--;
		else if(m['R']) ans+='R',m['R']--;
		else st=1;
		if(y>=0){
			while(m['D']){
			    ans+='D';
			    m['D']--;
			    yy--;
		    }
		}
		else{
			while(m['U']){
			    ans+='U';
			    m['U']--;
			    yy++;
		    }
		}
		while(m['D']){
			ans+='D';
			yy--;
			if(yy==y&&st){
				cout<<"Impossible"<<endl;
				return;
			}
			m['D']--;
		}
		while(m['U']){
		    ans+='U';
		    yy++;
		    if(yy==y&&st){
				cout<<"Impossible"<<endl;
				return;
			}
			 m['U']--;
		}
		while(m['L']) ans+='L', m['L']--;;
		while(m['R']) ans+='R', m['R']--;;
	}
	else if(y==0){
		int xx=0;
		bool st=0;
		if(m['U']) ans+='U',m['U']--;
		else if(m['D']) ans+='D',m['D']--;
		else st=1;
		if(x>=0){
			while(m['L']){
			    ans+='L';
			    xx--;
			    m['L']--;
		    }
		}
		else{
			while(m['R']){
			    ans+='R';
			    xx++;
			     m['R']--;
		    }
		}
		while(m['L']){
			ans+='L';
			xx--;
			if(xx==x&&st){
				cout<<"Impossible"<<endl;
				return;
			}
			 m['L']--;
		}
		while(m['R']){
		    ans+='R';
		    xx++;
		    if(xx==x&&st){
				cout<<"Impossible"<<endl;
				return;
			}
			 m['R']--;
		}
		while(m['L']) ans+='L', m['L']--;
		while(m['R']) ans+='R', m['R']--;
	}
	cout<<ans<<endl;
}
signed main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	int T=1;
	cin>>T;
	while(T--){
		solve();
	}
	return 0;
}