#include <bits/stdc++.h>

using namespace std;

int c[5];
int p[5];
int xc,yc;
map<char,int> mp1;
map<int,char> mp2;

bool check()
{
    int x=0,y=0;
    if(x==xc&&y==yc) return 0;
    for(int i=1;i<=4;i++)
    {
        int u=p[i];
        for(int j=1;j<=c[u];j++)
        {
            if(u==1) y++;
            else if(u==2) x--;
            else if(u==3) x++;
            else y--;
            if(x==xc&&y==yc) return 0;
        }
    }
    return 1;
}

void solve()
{
    cin >> xc >> yc;
    for(int i=1;i<=4;i++) c[i]=0;
    for(int i=1;i<=4;i++) p[i]=i;
    string s;
    cin >> s;
    for(auto x : s)
    {
        c[mp1[x]]++;
    }

    do
    {
        if(check())
        {
            // for(int i=1;i<=4;i++) cout << p[i] << " ";
            // cout << "\n";
            for(int i=1;i<=4;i++)
            {
                int x=p[i];
                char ss=mp2[x];
                for(int j=1;j<=c[x];j++) cout << ss;
            }
            cout << "\n";
            return;
        }
    }while(next_permutation(p+1,p+5));
    cout << "Impossible\n";
}

int main()
{
    mp1['U']=1;
    mp1['L']=2;
    mp1['R']=3;
    mp1['D']=4;
    mp2[1]='U';
    mp2[2]='L';
    mp2[3]='R';
    mp2[4]='D';
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int T;
    cin >> T;
    while(T--) solve();
    return 0;

}