#include<bits/stdc++.h>
using namespace std;
#define int long long
const int N = 2e3 + 5;
int a[N];
int b[N]; int n, m;
int c[N];
int coun[N];
double l[N], r[N];
void solve()
{

    int x, y;
    cin >> x >> y;
    string s;
    cin >> s;
    memset(a, 0, sizeof(a));
    for (int i = 0; i < s.size(); i++)
    {
        if (s[i] == 'U') a[0]++;
        if (s[i] == 'D') a[1]++;
        if (s[i] == 'L') a[2]++;
        if (s[i] == 'R') a[3]++;

    }
    if (((a[0] - a[1]) == y) && ((a[3] - a[2]) == x))
    {
        cout << "Impossible" << endl;
        return;
    }
    else if ((a[2] == 0 && a[3] == 0))
    {
        if (y >= 0 && a[0] - a[1] >= y)
        {
            cout << "Impossible" << endl;
            return;

        }
        if (y <= 0 && a[0] - a[1] <= y)
        {
            cout << "Impossible" << endl;
            return;

        }
    }
    else if ((a[0] == 0 && a[1] == 0))
    {
        if (x >= 0 && a[3] - a[2] >= x)
        {
            cout << "Impossible" << endl;
            return;

        }
        if (x <= 0 && a[3] - a[2] <= x)
        {
            cout << "Impossible" << endl;
            return;

        }
    }

    if (a[0] - a[1] == y)
    {
        if (y == 0)
        {
            cout << "U";
            for (int i = 0; i < a[3]; i++) cout << "R";
            for (int i = 0; i < a[2]; i++) cout << "L";
            for (int i = 0; i < a[0] - 1; i++) cout << "U";
            for (int i = 0; i < a[1]; i++) cout << "D";
        }
        else
        {
            for (int i = 0; i < a[3]; i++) cout << "R";
            for (int i = 0; i < a[2]; i++) cout << "L";
            for (int i = 0; i < a[1]; i++) cout << "D";
            for (int i = 0; i < a[0]; i++) cout << "U";
        }
    }
    else if (a[3] - a[2] == x)
    {
        for (int i = 0; i < a[1]; i++) cout << "D";
        for (int i = 0; i < a[0]; i++) cout << "U";
        for (int i = 0; i < a[3]; i++) cout << "R";
        for (int i = 0; i < a[2]; i++) cout << "L";
    }
    else
    {
        for (int i = 0; i < a[3]; i++) cout << "R";
        for (int i = 0; i < a[2]; i++) cout << "L";
        for (int i = 0; i < a[1]; i++) cout << "D";
        for (int i = 0; i < a[0]; i++) cout << "U";
    }
    cout << endl;

}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while (t--)
    {
        solve();
    }

}