#include<bits/stdc++.h>
using namespace std;
#define int long long
int x, y;
bool check( string s ){
    int X = 0, Y = 0;
    for(int i = 0; i < s.size(); i ++ ){
        if( s[i] == 'U' )
            Y ++;
        if( s[i] == 'D' )
            Y --;
        if( s[i] == 'L' )
            X --;
        if( s[i] == 'R' )
            X ++;
        if( X == x && Y == y ){
            return 0;
        }
    }
    return 1;
}
signed main(){
    int t;
    string s;
    cin >> t;
    while( t -- ){
        cin >> x >> y;
        cin >> s;
        if( x == 0 && y == 0 ){
            cout << "Impossible\n";
            continue;
        }
        int u = 0, d = 0, l = 0, r = 0;
        for(int i = 0; i < s.size(); i ++ ){
            if( s[i] == 'U' )
                    u ++;
            if( s[i] == 'D' )
                    d ++;
            if( s[i] == 'L' )
                    l ++;
            if( s[i] == 'R' )
                r ++;
        }
        string ans = "";
        int currx = 0, curry = 0;
        // zugtaj baigaa pussy pisda
        if( currx <= x ){
            for(int i = 1; i <= l; i ++ ){
                ans += "L";
                currx --;
            }
        }else{
            for(int i = 1; i <= r; i ++ ){
                ans += "R";
                currx ++;
            }
        }
        if( curry <= y ){
            for(int i = 1; i <= d; i ++ ){
                ans += "D";
                curry --;
            }
        }else{
            for(int i = 1; i <= u; i ++ ){
                ans += "U";
                curry ++;
            }
        }
        //tulah gej baigaa zorigtoi lalar
        string pisda = "";
        if( currx <= x ){
            for(int i = 1; i <= r; i ++ ){
                pisda += "R";
            }

        }else{
            for(int i = 1; i <= l; i ++ ){
                pisda += "L";
            }
        }
         string lalar = "";
        if( curry <= y ){
            for(int i = 1; i <= u; i ++ ){
                lalar += "U";
            }
        }else{
            for(int i = 1; i <= d; i ++ ){
                lalar += "D";
            }
        }
        if( check( ans + pisda + lalar ) ){
            cout << ans+pisda+lalar<<"\n";
            continue;
        }
        if( check( ans + lalar + pisda ) ){
            cout << ans + lalar + pisda << "\n";
            continue;
        }
        cout << "Impossible\n";
    }
}