#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N = 1e6 + 10;
int x, y;
string s;
int flag = 0;
int dir[5];
int ds[4] = { 1, 2, 3, 4 };
char dp[5] = { '0', 'R', 'L', 'U', 'D' };

bool check() {
    int x1 = 0, y1 = 0;
    if (x == 0 && y == 0)return false;
    for (int i = 0; i <= 3; i++) {
        if (ds[i] == 1) {
            if (y1 == y && x1 <= x && x1 + dir[1] >= x) return false;
            x1 += dir[1];
        }
        if (ds[i] == 2) {
            if (y1 == y && x1 >= x && x1 - dir[2] <= x) return false;
            x1 -= dir[2];
        }
        if (ds[i] == 3) {
            if (x1 == x && y1 <= y && y1 + dir[3] >= y) return false;
            y1 += dir[3];
        }
        if (ds[i] == 4) {
            if (x1 == x && y1 >= y && y1 - dir[4] <= y) return false;
            y1 -= dir[4];
        }
    }
    return true;
}

void solve() {
    flag = 0;
    cin >> x >> y;
    cin >> s;
    dir[1] = count(s.begin(), s.end(), 'R');
    dir[2] = count(s.begin(), s.end(), 'L');
    dir[3] = count(s.begin(), s.end(), 'U');
    dir[4] = count(s.begin(), s.end(), 'D');

    do {
        if (check()) {
            flag = 1;
            for (int i = 0; i <= 3; i++) {
                for (int j = 0; j < dir[ds[i]]; j++)
                    cout << dp[ds[i]];
            }
            break;
        }
    } while (next_permutation(ds, ds + 4));

    if (!flag)
        cout << "Impossible";
    cout << endl;
}

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