#include<bits/stdc++.h>
const int N=1e3+10;
const int M=2e6+10;
#define int long long
typedef double db;
typedef long long ll;
using namespace std;
using pii = pair<int,int>;
#define up(i,a,b) for(int i=(a);i<=(b);++i)
#define down(i,a,b) for(int i=(a);i>=(b);--i)
#define puts(a) (cout<<a<<endl)
#define inf (0x7fffffff)
const int MOD=100003;
int xx,yy;
int d[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
int u[4];
int a[]={0,1,2,3};
bool check(){
	int aa=0,bb=0;
			//aa行，bb列
			for(int i=0;i<4;i++){
				for(int j=0;j<u[a[i]];j++){
					aa+=d[a[i]][0];
					bb+=d[a[i]][1];
					if(aa==xx&&bb==yy)
                        return false;
				}
			}
			return true;
}



void solve(){
	string s;
		cin>>xx>>yy;
		int x=0,y=0;
		int flag=0;
		if(xx==0&&yy==0){
            cout<<"Impossible"<<endl;
            flag=1;


		}

		cin>>s;
		if(flag)
                return ;
		memset(u,0,sizeof u);
		for(int i=0;s[i];i++){
			if(s[i]=='U')u[0]++,y++;
			else if(s[i]=='D')
                u[1]++,x++;
			else if(s[i]=='R')
			u[2]++,y--;
			else if(s[i]=='L')
			u[3]++,x--;
		}
		if(x==xx&&y==yy){
			cout<<"Impossible"<<endl;
			return ;
		}
		int ok=1;
		for(int i=1;i<24;i++){

			if(check()){
				for(int i=0;i<4;i++){
					for(int j=0;j<u[a[i]];j++){
						if(a[i]==0)cout<<"U";
						else if(a[i]==1)cout<<"D";
						else if(a[i]==2)cout<<"R";
						else if(a[i]==3)cout<<"L";
					}
				}
				ok=0;
				break;
			}

			next_permutation(a,a+4);
		}
		if(ok){
			cout<<"Impossible";
		}
		cout<<endl;

}

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