#include<bits/stdc++.h>
#define LL long long
#define P pair<int,int>
#define fi first
#define se second
#define fr(x) freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);
using namespace std;
const int N=1e5+5,dx[]={0,-1,1,0},dy[]={1,0,0,-1};const char To[]={'U','L','R','D'};
int T,c[7],cc[7],mx,my,x,y;string C,ans,ans1;
inline int to(char x)
{
	if(x=='U') return 0;if(x=='D') return 3;
	if(x=='L') return 1;if(x=='R') return 2;
}
inline void sol()
{
	basic_string<int>g;g.clear();
	for(int i=0;i<4;i++) if(c[i]) g+=i;x=0,y=0;
	if(!g.size()) return cout<<ans<<"\n",void();
	if(g.size()==1)
	{
		int t=g[0];bool ok=1;
		for(int i=1;i<=c[t];i++)
		{
			x+=dx[t],y+=dy[t];
			if(x==mx&&y==my){ok=0;break;}
		}
		if(ok)
		{
			for(int i=1;i<=c[t];i++) ans+=To[t];
			cout<<ans<<"\n";return;	
		}int t1=t;
		g.clear();
		for(int i=0;i<4;i++) if(i!=t&&i!=3-t) g+=i;
		ok=1;
		for(int i:g) if(!cc[i]){ok=0;break;}
		if(!ok) return cout<<"Impossible\n",void();
		ans1+=To[g[0]];
		for(int i=1;i<=c[t];i++) ans1+=To[t1];
		ans1+=To[g[1]];bool O[4];memset(O,0,sizeof(O));
		for(char i:ans)
		{
			int too=to(i);
			if(!O[too])
			{
				O[too]=1;
				if(too!=g[0]&&too!=g[1]) cout<<i;
			}
			else cout<<i;
		}cout<<ans1<<"\n";return;
	}
	
	bool ok=1;int t=g[0];
	for(int i=1;i<=c[t];i++)
	{
		x+=dx[t],y+=dy[t];
		if(x==mx&&y==my){ok=0;break;}
	}
	if(!ok) swap(g[0],g[1]);t=g[0];
	for(int i=1;i<=c[t];i++) ans+=To[t];t=g[1];
	for(int i=1;i<=c[t];i++) ans+=To[t];cout<<ans<<"\n";
}
int main()
{
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);cin>>T;
	while(T--)
	{
		memset(c,0,sizeof(c));cin>>mx>>my>>C;
		if(!mx&&!my){cout<<"Impossible\n";continue;}
		for(char x:C) c[to(x)]++;x=0,y=0;memcpy(cc,c,sizeof(c));
		for(int i=0;i<4;i++) x+=dx[i]*c[i],y+=dy[i]*c[i];
		if(x==mx&&y==my){cout<<"Impossible\n";continue;}ans=ans1="";
		int mn=min(c[0],c[3]),X=0,Y=3;
		if(dx[X]==mx&&dy[X]==my) swap(X,Y);
		for(int i=1;i<=mn;i++) ans+=To[X],ans+=To[Y];
		c[0]-=mn,c[3]-=mn;
		mn=min(c[1],c[2]);X=1,Y=2;
		if(dx[X]==mx&&dy[X]==my) swap(X,Y);
		for(int i=1;i<=mn;i++) ans+=To[X],ans+=To[Y];
		c[1]-=mn,c[2]-=mn;

		sol();
	}
	return 0;
}