// Narcissus & ?????????

#include <bits/stdc++.h>
using i64 = long long;

//{{{????
template<typename Ta, typename Tb>
inline void chkmax(Ta &a, const Tb &b) {if (a < b)	a = b;}
template<typename Ta, typename Tb>
inline void chkmin(Ta &a, const Tb &b) {if (a > b)	a = b;}
//}}}

const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, 1, 0, -1};

int cnt[4];
int p[4];

void solve() {
	int x, y;
	std::string s;
	std::cin >> x >> y;
	std::cin >> s;
	memset(cnt, 0, sizeof(cnt));
	for (const char &c : s) {
		if (c == 'L')
			cnt[0]++;
		if (c == 'U')
			cnt[1]++;
		if (c == 'R')
			cnt[2]++;
		if (c == 'D')
			cnt[3]++;
	}

	auto check = [&]() -> bool {
		int cx = 0, cy = 0;
		if (cx == x && cy == y) {
			return false;
		}

		for (int i = 0; i < 4; i++) {
			for (int t = 0; t < cnt[p[i]]; t++) {
				cx += dx[p[i]];
				cy += dy[p[i]];
				if (cx == x && cy == y)
					return false;
			}
		}
		return true;
	};


	for (int i = 0; i < 4; i++)	p[i] = i;
	int pcount = 4 * 3 * 2 * 1;
	while (pcount--) {
		if (check()) {
			for (int i = 0; i < 4; i++) {
				for (int t = 0; t < cnt[p[i]]; t++) {
					if (p[i] == 0)
						std::cout << "L";
					if (p[i] == 1)
						std::cout << "U";
					if (p[i] == 2)
						std::cout << "R";
					if (p[i] == 3)
						std::cout << "D";
				}
			}
			std::cout << '\n';
			return ;
		}
		std::next_permutation(p, p + 4);
	}
	std::cout << "Impossible" << '\n';
}

int main() {
#ifdef HeratinoNelofus
	freopen("input.txt", "r", stdin);
#endif
	std::ios::sync_with_stdio(false);
	std::cin.tie(nullptr);

	int T;
	std::cin >> T;
	while (T--) {
		solve();
	}
	return 0;
}