# include <bits/stdc++.h>
using namespace std;

# ifndef ONLINE_JUDGE
# include "debug.h"
# else
# define debug(...) 0721
# define ps 0721
# endif

using i32 = signed;
using i64 = long long;

void solve() {
    array<int, 4> cnt{};
    array<int, 2> v{};
    cin >> v[0] >> v[1];
    string s;
    cin >> s;
    for (char v : s) {
        if (v == 'U') {
            cnt[0] ++;
        } else if (v == 'D') {
            cnt[1] ++;
        } else if (v == 'L') {
            cnt[2] ++;
        } else {
            cnt[3] ++;
        }
    }
    array<int, 4> ord{};
    iota(ord.begin(), ord.end(), 0);
    bool finded = false;
    do {
        array<int, 2> u{};
        bool ok = true;
        for (auto c : ord) {
            if (c == 0) {
                if (u[0] == v[0] && u[1] <= v[1] && v[1] <= u[1] + cnt[c]) {
                    ok = false;
                    break;
                }
                u[1] += cnt[c];
            } else if (c == 1) {
                if (u[0] == v[0] && u[1] - cnt[c] <= v[1] && v[1] <= u[1]) {
                    ok = false;
                    break;
                }
                u[1] -= cnt[c];
            } else if (c == 2) {
                if (u[0] - cnt[c] <= v[0] && v[0] <= u[0] && u[1] == v[1]) {
                    ok = false;
                    break;
                }
                u[0] -= cnt[c];
            } else {
                if (u[0] <= v[0] && v[0] <= u[0] + cnt[c] && u[1] == v[1]) {
                    ok = false;
                    break;
                }
                u[0] += cnt[c];
            }
        }
        if (ok) {
            finded = true;
            break;
        }
    } while (next_permutation(ord.begin(), ord.end()));
    if (finded) {
        string s;
        for (auto c : ord) {
            if (c == 0) {
                s += string(cnt[c], 'U');
            } else if (c == 1) {
                s += string(cnt[c], 'D');
            } else if (c == 2) {
                s += string(cnt[c], 'L');
            } else {
                s += string(cnt[c], 'R');
            }
        }
        cout << s;
    } else {
        cout << "Impossible";
    }
}

i32 main() {
    ios::sync_with_stdio(0);
    cin.tie(0);

# ifndef ONLINE_JUDGE
    freopen("Input.txt", "r", stdin);
    freopen("Output.txt", "w", stdout);
    freopen("Error.txt", "w", stderr);
# endif

    i32 t = 1;
    cin >> t;
    while (t --) {
        solve();
        if (t != 0) {
            cout << '\n';
        }
    }
    return 0;
}