#include <bits/stdc++.h>

/* Orther */
#define int long long
#define YES cout<<"YES\n"
#define NO cout<<"NO\n"
#define IOS ios::sync_with_stdio(false);cin.tie(0); cout.tie(0)
using namespace std;

/* Pair */
#define x first
#define y second

/* Data type */
using ll = long long;
using ull = unsigned long long;
using PII = pair<int,int>;
using VI = vector<int>;

/* STL */
#define eb emplace_back
#define ef emplace_front
#define pb push_back
#define pf push_front
#define mp make_pair
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define all1(x) x.begin()+1,x.end()

/* Random */
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define random(a,b) rng()%(b-a+1)+a

/* Contest */
const int INF = 0x3f3f3f3f ; // 1e9
const int MOD =  998244353 ;
const int N = 2e5 + 10, M = 55;

char g[20][20];
void Rainbow_()
{
	int mx , my;
	cin >> mx >> my;
	int tmp = 0;
	tmp = mx;
	mx = my; my = tmp ;
	string s; cin >> s;
	int n = s.size();
	
	int u = 0, d = 0, l = 0, r = 0;
	for (int i = 0 ; i < n ; i ++ ) {
		if (s[i] =='U') {
			u ++ ;
		} else if (s[i] == 'D' ) {
			d ++ ;
		} else if (s[i] == 'L' ) {
			l ++ ;
		} else if (s[i] == 'R' ) {
			r ++ ;
		}
	}
	
	if ( (u - d == my && r - l == mx) || (mx == 0 && my == 0) ) {
		cout << "Impossible\n";
    	return ;
	}
	
	string p = "?1234";
	// u 1 / d 2 / l 3 / r 4
	string ans = "";
	bool judge = false ;
	do {
		int nowx = 0 , nowy = 0; bool ok = true ;
		for (int i = 1 ; i <= 4; i ++ ) {
			//cout << nowx << ' ' << nowy << '\n';
			if ( p[i] == '1' ) {
				if ( nowy == my && mx >= nowx && nowx + u >= mx ) {
					ok = false ;
					break ;
				}
			} else if ( p[i] == '2' ) {
				if ( nowy == my && mx <= nowx && nowx - d <= mx) {
					ok = false ;
					break ;
				}
			} else if ( p[i] == '3' ) {
				if ( nowx == mx && my >= nowy - l && my <= nowy ) {
					ok = false ;
					break ;
				}
			} else if ( p[i] == '4' ) {
				if ( nowx == mx && my <= nowy + r && my >= nowy ) {
					ok = false ;
					break ;
				}
			} // 四种会达到炸弹的情况
			if ( p[i] == '1' ) {
				nowx += u;
			} else if ( p[i] == '2' ) {
				nowx -= d;
			} else if ( p[i] == '3' ) {
				nowy -= l;
			} else if ( p[i] == '4' ) {
				nowy += r;
			}
		}
		
		if ( ok ) {
			for (int i = 1; i <= 4; i ++ ) {
				if ( p[i] == '1' ) {
					for (int i = 0; i < u; i ++ ) {
						ans.pb('U');
					}
				} else if ( p[i] == '2' ) {
					for (int i = 0; i < d; i ++ ) {
						ans.pb('D');
					}
				} else if ( p[i] == '3' ) {
					for (int i = 0; i < l; i ++ ) {
						ans.pb('L');
					}
				} else if ( p[i] == '4' ) {
					for (int i = 0; i < r; i ++ ) {
						ans.pb('R');
					}
				}
			}
			judge = true ;
			cout << ans << '\n';
			break ;
		}
		
	} while ( next_permutation( all1(p) ) );
	
	if ( !judge ) {
		cout << "Impossible\n";
    	return ;
	}
	
	return ;
}
 
signed main()
{   
    IOS;
    int _ = 1;
    cin >> _;
 
    while ( _ -- ) 
        Rainbow_();
 
    return 0;
}