#include <bits/stdc++.h>
using namespace std;
bool check(string s,int x,int y)
{
	int x1=0,y1=0;
	for (int i=0;i<s.size();i++)
	{
		if (x1==x&&y1==y)
		{
			return false;
		}
		if (s[i]=='U') y1++;
		if (s[i]=='D') y1--;
		if (s[i]=='L') x1--;
		if (s[i]=='R') x1++;
	}
	if (x1==x&&y1==y)
	{
		return false;
	}
	return true;
}
void solve()
{
	int x,y;
	cin>>x>>y;
	int n=0,m=0;
	int x1=0,y1=0;
	string s;
	cin>>s;
	int len=s.size();
	for (int i=0;i<s.size();i++)
	{
		if (s[i]=='U') m++;
		if (s[i]=='D') m--;
		if (s[i]=='L') n--;
		if (s[i]=='R') n++;
	}
	// cout<<n<<" "<<m<<" "<<x<<" "<<y<<endl;
	int flag=check(s,x,y);
	if (flag)
	{
		cout<<s<<endl;
		return ;
	}
	if (x==n&&y==m)
	{
		cout<<"Impossible"<<endl;
		return ;
	}
	if (x==0&&y==0)
	{
		cout<<"Impossible"<<endl;
		return ;
	}
	if (n==0)
	{
		// cout<<len<<" "<<y<<endl;
		if (len-abs(m)==0)
		{
			cout<<"Impossible"<<endl;
			return ;
		}
		string s1="",s2="";
		int k=(len-abs(y))/2;
		for (int i=1;i<=len;i++)
		{
			if (i<=k)
			{
				s1+='L';
				s2+='R';
			}
			else if(i>len-k)
			{
				s1+='R';
				s2+='L';
			}
			else
			{
				if (y>0)
				{
					s1+='U',s2+='U';
				}
				else
				{
					s1+='D',s2+='D';
				}
			}
		}
		flag=check(s1,x,y);
		if (flag)
		{
			cout<<s1<<endl;
			return ;
		}
		cout<<s2<<endl;
		return ;
	}
	if (m==0)
	{
		if (len-abs(m)==0)
		{
			cout<<"Impossible"<<endl;
			return ;
		}
		string s1="",s2="";
		int k=(len-abs(x))/2;
		// cout<<k<<endl;
		for (int i=1;i<=len;i++)
		{
			if (i<=k)
			{
				s1+='U';
				s2+='D';
			}
			else if(i>len-k)
			{
				s1+='D';
				s2+='U';
			}
			else
			{
				if (x>0)
				{
					s1+='R',s2+='R';
				}
				else
				{
					s1+='L',s2+='L';
				}
			}
		}
		flag=check(s1,x,y);
		if (flag)
		{
			cout<<s1<<endl;
			return ;
		}
		cout<<s2<<endl;
		return ;
	}
	if (len>abs(n)+abs(m))
	{
		if (x!=0||y!=1)
		{
			for (int i=1;i<=len-abs(n)-abs(m);i++)
			{
				if (i%2==1)
				{
					cout<<"U";
				}
				else
				{
					cout<<"D";
				}
			}
		}
		else
		{
			for (int i=1;i<=len-abs(n)-abs(m);i++)
			{
				if (i%2==1)
				{
					cout<<"D";
				}
				else
				{
					cout<<"U";
				}
			}
		}
	}
	if (n>0)
	{
		string s1="",s2="";
		for (int i=1;i<=n;i++)
		{
			s1+='R';
		}
		if (m>0)
		{
			for (int i=1;i<=m;i++)
			{
				s1+='U';
				s2+='U';
			}
		}
		else
		{
			for (int i=1;i<=abs(m);i++)
			{
				s1+='D';
				s2+='D';
			}
		}
		for (int i=1;i<=n;i++)
		{
			s2+='R';
		}
		flag=check(s1,x,y);
		if (flag)
		{
			cout<<s1<<endl;
			return ;
		}
		cout<<s2<<endl;
		return ;
	}
	if (n<0)
	{
		string s1="",s2="";
		for (int i=1;i<=abs(n);i++)
		{
			s1+='L';
		}
		if (m>0)
		{
			for (int i=1;i<=m;i++)
			{
				s1+='U';
				s2+='U';
			}
		}
		else
		{
			for (int i=1;i<=abs(m);i++)
			{
				s1+='D';
				s2+='D';
			}
		}
		for (int i=1;i<=abs(n);i++)
		{
			s2+='L';
		}
		flag=check(s1,x,y);
		if (flag)
		{
			cout<<s1<<endl;
			return ;
		}
		cout<<s2<<endl;
		return ;
	}
}
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		solve();
	}
	return 0;
}