#include <bits/stdc++.h>

using namespace std;
int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};


void solve()
{
    int x,y;cin>>x>>y;
    string s;cin>>s;
    string ans = "";
    int len=s.size();
    map<char,int> mp;
    int edx=0,edy=0;
    map<int, char> p;
    p[0] = 'U', p[1] = 'R', p[2] = 'D', p[3] = 'L';


    for(int i=0;i<s.size();i++) {
        mp[s[i]]++;
        if(s[i]=='R') {
            edx++;
        }
        else if(s[i]=='L') {
            edx--;
        }
        else if(s[i]=='U') {
            edy++;
        }
        else {
            edy--;
        }
    }


    if(edx==x&&edy==y||x==0&&y==0) {
        cout<<"Impossible"<<endl;
        return ;
    } 
    int sum1=mp['R'],sum2=mp['L'],sum3=mp['U'],sum4=mp['D'];
    if((sum3-sum4)>=y&&y>=0&&x==0&&sum1==0&&sum2==0) {
        cout<<"Impossible"<<endl;
        return ;
    }
    if((sum1-sum2)>=x&&x>=0&&y==0&&sum3==0&&sum4==0) {
        cout<<"Impossible"<<endl;
        return ;
    }
    if((sum4-sum3)>=abs(y)&&y<=0&&x==0&&sum1==0&&sum2==0) {
        cout<<"Impossible"<<endl;
        return ;
    }
    if((sum2-sum1)>=abs(x)&&x<=0&&y==0&&sum3==0&&sum4==0) {
        cout<<"Impossible"<<endl;
        return ;
    }
    int ex=0,ey=0;


    for (int i = 0; i < s.size(); i ++){

        for (int j = 0; j < 4; j ++){
            // if (i == 2){
            //     cout << j << endl;

            // }
            if (!mp[p[j]]) continue;

            int tx = ex + dx[j], ty = ey + dy[j];
            
            if (tx != x || ty != y){
                ex = tx, ey = ty;
                ans += p[j];
                mp[p[j]] --;
                swap(p[0], p[1]);
                swap(p[1], p[3]);
                break;
            }
            // reverse(a, a + n);
            

        }
        // cout << ex << ' ' << ey << endl;

    }

    cout << ans << endl;


}
int main()
{
    int t;
    cin>>t;
    while(t--){
        solve();
    }
    return 0;
}