#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--)
const int N=1e6+10;
const int M=1e2+10;
int mod=998244353;
int a[N];
int f[M][M];
int xx,yy;
int n,m;
string s;
int d[4];
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
string ss="";
int fg=0;
void dfs(int x,int y,int step){
	if(step==s.size()){
		fg=1;
		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);
		s.erase(s.size()-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]--;
	}
	
	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];
		}
	}
	dfs(0,0,0);
	
	cout<<ss<<endl;
	ss.clear();
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0),cout.tie(0);
	int n=1;
	cin>>n;
	while(n--)
	solve();
	return 0;
}