#include <bits/stdc++.h>

using i64 = long long;

const std::map<char, int> ID = {{'U', 0}, {'D', 1}, {'L', 2}, {'R', 3}};
const int dx[] = {0, 0, -1, 1};
const int dy[] = {1, -1, 0, 0};

void solve() {
    int tx, ty;
    std::cin >> tx >> ty;

    std::string s;
    std::cin >> s;

    if (tx == 0 && ty == 0) {
        std::cout << "Impossible\n";
        return;
    }

    std::array<int, 4> cnt{};
    for (auto c : s) {
        cnt[ID.at(c)] += 1;
    }

    auto check = [&](const std::string &s) {
        int x = 0, y = 0;
        for (auto c : s) {
            x += dx[ID.at(c)];
            y += dy[ID.at(c)];
            if (x == tx && y == ty) {
                return false;
            }
        }
        return true;
    };

    std::array<int, 4> p{0, 1, 2, 3};
    do {
        s.clear();
        for (auto x : p) {
            s += std::string(cnt[x], "UDLR"[x]);
        }
        if (check(s)) {
            std::cout << s << "\n";
            return;
        }
    } while (std::next_permutation(p.begin(), p.end()));

    std::cout << "Impossible\n";
}

int main() {
    std::cin.tie(nullptr)->sync_with_stdio(false);

    int t;
    std::cin >> t;

    while (t--) {
        solve();
    }

    return 0;
}