#include<bits/stdc++.h>
using namespace std;
const int N=200010;

void solve(){
	int mx,my,xx=0,yy=0,cnt=0;
	string s,str;
	vector<int> a(10);
	cin>>mx>>my>>s;
	for(char i:s){
		if(i=='U') a[1]++;
		if(i=='D') a[2]++;
		if(i=='L') a[3]++;
		if(i=='R') a[4]++;
	}
	// cout<<a[1]<<" "<<a[2]<<" "<<a[3]<<" "<<a[4]<<"\n";
	if(mx==0&&my==0){
		cout<<"Impossible\n";
		return ;
	}
	if(mx!=0){
		str=string(a[1],'U')+string(a[2],'D');
		if(mx>0) str+=string(a[3],'L')+string(a[4],'R');
		else str+=string(a[4],'R')+string(a[3],'L');
	}
	else{
		str=string(a[3],'L')+string(a[4],'R');
		if(my>0) str+=string(a[2],'D')+string(a[1],'U');
		else str+=string(a[1],'U')+string(a[2],'D');
	}
	for(char i:str){
		if(i=='U') yy++;
		if(i=='D') yy--;
		if(i=='L') xx--;
		if(i=='R') xx++;
		if(xx==mx&&yy==my) cnt=1;	
	}
	if(cnt) cout<<"Impossible\n";
	else cout<<str<<"\n";
}

int main(){
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	int T=1;
	cin>>T;
	while(T--){
		solve();
	}
	return 0;
}