#include <bits/stdc++.h>
using namespace std;
#define int long long
//#define endl "\n"
#define PII pair<int,int>
#define PIS pair<int,string>
#define fr(i,x,y) for(int i=x,p=y;i<=p;i++)
#define rp(i,x,y) for(int i=x,p=y;i>=p;i--)
map<int,string> mp;
const int N=1e6+10;
const int M=1e2+10;
int mod=998244353;
int xx,yy;
int n,m;

int d[4];
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
string ss="";
int fg=0;
string s;
void dfs(int x,int y,int step){
	if(step==s.size()){
		fg=1;
		cout<<ss<<endl;
		return;
	}if(fg){
		return;
	}
	fr(i,0,3){
		if(!d[i])continue;
		x+=dx[i];
		y+=dy[i];
		if(x==n&&y==m){
			continue;
		}
		d[i]--;
		if(i==1)ss+="R";
		if(i==0)ss+="U";
		if(i==3)ss+="L";
		if(i==2)ss+="D";
		dfs(x,y,step+1);
		if(fg)return;
		d[i]++;
		x-=dx[i];
		y-=dy[i];
		if(!ss.empty())ss.erase(ss.size()-1,1);
	}
}
void solve(){
	
	
	cin>>n>>m;
	fr(i,0,3){
		d[i]=0;
	}
	cin>>s;
	fr(i,0,s.size()-1){
		if(s[i]=='L')d[3]--;
		if(s[i]=='R')d[1]++;
		if(s[i]=='U')d[0]++;
		if(s[i]=='D')d[2]--;
	}
	mp[0]="U";
	mp[1]="R";
	mp[2]="D";
	mp[3]="L";
	
	if(n==0&&m==0){
		cout<<"Impossible"<<endl;
		return;
	}
	int cnt=0,now;
	int f[4]={0};
	fr(i,0,3){
		if(d[i]!=0&&!f[i]){
			cnt++;
			f[i]=1;
			now=i;
		}
	}
	int x=0,y=0;
	if(cnt==1){
		if(now%2){
			if(m==0&&(n>=min(0ll,d[now])&&n<=max(0ll,d[now]))){
				cout<<"Impossible"<<endl;
				return;
			}else{
				cout<<s<<endl;
				return;
			}
		}
		else{
			if(n==0&&(m>=min(0ll,d[now])&&m<=max(0ll,d[now]))){
				cout<<"Impossible"<<endl;
				return;
			}else{
				cout<<s<<endl;
				return;
			}
		}
	}
	fr(i,0,3){
		if(i%2)x+=d[i];
		else y+=d[i];
	}
	if(x==n&&y==m){
		cout<<"Impossible"<<endl;
		return;
	}
	fr(i,0,3){
		if(d[i]<0){
			d[i]=-d[i];
		}
	}
	int p=0;
	if(n>0){
		fr(i,1,d[3])cout<<"L";
		p+=d[3];
		x-=d[3];
		d[3]=0;
	}else{
		fr(i,1,d[1])cout<<"R";
		p+=d[1];
		x+=d[1];
		d[1]=0;
	}
	if(m>0){
		fr(i,1,d[2])cout<<"D";
		p+=d[2];
		y-=d[2];
		d[2]=0;
	}else{
		fr(i,1,d[0])cout<<"U";
		p+=d[0];
		y+=d[0];
		d[0]=0;
	}
	if(d[1]){
		int t=min(n-x-1,d[1]);
		fr(i,1,t)cout<<mp[1];
		d[1]-=t;
		if(d[0])fr(i,1,d[0])cout<<mp[0];
		if(d[2])fr(i,1,d[2])cout<<mp[2];
		d[0]=d[2]=0;
	}if(d[3]){
		int t=min(x-n-1,d[3]);
		fr(i,1,t)cout<<mp[3];
		d[3]-=t;
		if(d[0])fr(i,1,d[0])cout<<mp[0];
		if(d[2])fr(i,1,d[2])cout<<mp[2];
		d[0]=d[2]=0;
	}
	fr(i,0,3){
		if(d[i]){
			fr(j,1,d[i]){
				cout<<mp[i];
			}
		}
	}
	cout<<endl;

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