#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;
    }

    auto get = [&](char x, char y) {
        std::string a;
        int cx = int(std::count(s.begin(), s.end(), x));
        int cy = int(std::count(s.begin(), s.end(), y));
        if (cx < cy) {
            std::swap(x, y);
            std::swap(cx, cy);
        }
        for (int i = 0; i < cy; ++i) {
            a += x;
            a += y;
        }
        a += std::string(cx - cy, x);
        return a;
    };
    std::string a = get('U', 'D');
    std::string b = get('L', 'R');

    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;
            }
        }
        std::cout << s << "\n";
        return true;
    };
    if (!check(a + b) && !check(b + a)) {
        std::cout << "Impossible\n";
    }
}

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

    int t;
    std::cin >> t;

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

    return 0;
}