#include <bits/stdc++.h>
using namespace std;
#define IOS ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#define endl '\n'
const int N = 2e5 + 5;
#define int long long
typedef pair<int, int> PII;
#define MAX LONG_LONG_MAX
#define mod 10007
#define eps 1e-7
int l, r, d, u, a, b;
int ar[4] = {0, 1, 2, 3};
int cnt[4] = {0};
int op[4][2] = {{0, 1}, {0, -1}, {-1, 0}, {1, 0}};
map<int, char> mp;

bool check()
{
    int x = 0, y = 0;
    for (int i = 0; i < 4; i++)
        for (int j = 0; j < cnt[ar[i]]; j++)
        {
            x += op[ar[j]][0];
            y += op[ar[j]][1];
            if (x == a && y == b)
                return 0;
        }
    return 1;
}
void solve()
{

    cin >> a >> b;
    string s;
    cin >> s;
    int x = 0, y = 0;
    memset(cnt, 0, sizeof cnt);
    ar[0] = 0, ar[1] = 1, ar[2] = 2, ar[3] = 3;

    for (char c : s)
    {
        if (c == 'U')
            cnt[0]++, y++;
        else if (c == 'D')
            cnt[1]++, y--;
        else if (c == 'L')
            cnt[2]++, x--;
        else if (c == 'R')
            cnt[3]++, x++;
    }
    if (x == a && y == b || a == 0 && b == 0)
    {
        cout << "Impossible" << endl;
        return;
    }
    bool ok = 0;

    do
    {
        if (check())
        {
            ok = 1;
            for (int i = 0; i < 4; i++)
                for (int j = 0; j < cnt[ar[i]]; j++)
                    cout << mp[ar[i]];
            break;
        }
    } while (next_permutation(ar, ar + 4));
    if (!ok)
    {
        cout << "Impossible" << endl;
    }
}

signed main()
{
    mp[0] = 'U';
    mp[1] = 'D';
    mp[2] = 'L';
    mp[3] = 'R';

    int t;
    cin >> t;
    while (t--)
        solve();

    return 0;
}