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

#define int long long  

string d1 = "ULDR", d2 = "DRUL";
void solve()
{
	int sx, sy;
	cin >> sx >> sy;
	string s;
	cin >> s;

	if(sx == 0 && sy == 0) {
		cout << "Impossible\n";
		return ;
	}

	map<char, int> cnt;
	for(auto &c : s) {
		++cnt[c];
	}

	int x, y;
	bool ok;

	auto mv = [&](char dir, int dis) {
		if(dir == 'U') {
			if(sx == x) {
				if(y <= sy && sy <= y + dis)
					return false;
			}
			y += dis;
		} else if(dir == 'L') {
			if(sy == y) {
				if(x >= sx && sx >= x - dis)
					return false;
			}
			x -= dis;
 		} else if(dir == 'D') {
			if(sx == x) {
				if(y >= sy && sy >= y - dis)
					return false;
			}
			y -= dis;
		} else if(dir == 'R') {
			if(sy == y) {
				if(x <= sx && sx <= x + dis)
					return false;
			}
			x += dis;			
		}
		return true;
	}; 

	x = 0, y = 0;
	ok = 1;
	for(auto &c : d1) {
		ok &= mv(c, cnt[c]);
	}
	if(ok) {
		for(auto &c : d1) {
			for(int i = 0; i < cnt[c]; ++i)
				cout << c;
		}
		cout << '\n';
		return ;
	}

	x = 0, y = 0;
	ok = 1;
	for(auto &c : d2) {
		ok &= mv(c, cnt[c]);
	}
	if(ok) {
		for(auto &c : d2) {
			for(int i = 0; i < cnt[c]; ++i)
				cout << c;
		}
		cout << '\n';
		return ;
	}

	
	cout << "Impossible\n";
}


signed main() {  
    ios::sync_with_stdio(false);
    cin.tie(nullptr);  

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