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

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

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