#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
using namespace std;

const int MAXN = 1e5 + 10;
char str[MAXN];
int mx, my;
bool used[MAXN];

int main() {
	int t; scanf("%d", &t);
	for (int u = 1; u <= t; u++) {
		scanf("%d %d", &mx, &my);
		scanf("%s", str + 1);
		bool flag = true;
		int n = strlen(str + 1);
		for (int i = 1; i <= n; i++) used[i] = false;
		for (int i = 1; i <= n; i++) {
			if (str[i] != 'U' && str[i] != 'D') {
				flag = false;
				break;
			}
		}
		if (flag) { //UD
			if (mx != 0) printf("%s\n", str + 1);
			else {
				int End = 0;
				for (int i = 1; i <= n; i++) {
					if (str[i] == 'U') End++;
					else End--;
				}
				if (my > 0) {
					if (End >= my) printf("Impossible\n");
					else {
						for (int i = 1; i <= n; i++) {
							if (str[i] == 'D') printf("D");
						}
						for (int i = 1; i <= n; i++) {
							if (str[i] == 'U') printf("U");
						}
						printf("\n");
					}
				} else if (my < 0) {
					if (End <= my) printf("Impossible\n");
					else {
						for (int i = 1; i <= n; i++) {
							if (str[i] == 'U') printf("U");
						} 
						for (int i = 1; i <= n; i++) {
							if (str[i] == 'D') printf("D");
						}
						printf("\n");
					}
				} else 
					printf("Impossible\n");
			}
		} else {
			flag = true;
			for (int i = 1; i <= n; i++) {
				if (str[i] != 'L' && str[i] != 'R') {
					flag = false;
					break;
				}
			}
			if (flag) { //LR 
				if (my != 0) printf("%s\n", str + 1);
				else {
					int End = 0;
					for (int i = 1; i <= n; i++) {
						if (str[i] == 'L') End--;
						else End++;
					}
					if (mx < 0) {
						if (End <= mx) printf("Impossible\n");
						else {
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'R') printf("R");
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L') printf("L");
							}
							printf("\n");
						}
					} else if (mx > 0) {
						if (End >= mx) printf("Impossible\n");
						else {
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L') printf("L");
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'R') printf("R");
							}
							printf("\n");
						}
 					} else 
						printf("Impossible\n");
				}
			} else {
				int End1 = 0, End2 = 0;
				for (int i = 1; i <= n; i++) {
					if (str[i] == 'U') End1++;
					if (str[i] == 'D') End1--;
					if (str[i] == 'L') End2--;
					if (str[i] == 'R') End2++;
				} 
				if (my == End1 && mx == End2) printf("Impossible\n");
				else if (mx == 0 && my == 0) printf("Impossible\n");
				else {
					if (my != End1) {
						if (mx != 0) {
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'U' || str[i] == 'D')
									printf("%c", str[i]);
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L' || str[i] == 'R') 
									printf("%c", str[i]);
							}
							printf("\n");
						} else {
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L' || str[i] == 'R')  {
									printf("%c", str[i]);
									used[i] = true;
									break;
								}
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'U' || str[i] == 'D')
									printf("%c", str[i]);
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L' || str[i] == 'R') 
									if (!used[i])
										printf("%c", str[i]);
							}
						}
					} else {
						if (my != 0) {
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L' || str[i] == 'R') 
									printf("%c", str[i]);
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'U' || str[i] == 'D')
									printf("%c", str[i]);
							}
							printf("\n");
						} else {
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'U' || str[i] == 'D') {
									printf("%c", str[i]);
									used[i] = true;
									break;
								}
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'L' || str[i] == 'R') 
									printf("%c", str[i]);
							}
							for (int i = 1; i <= n; i++) {
								if (str[i] == 'U' || str[i] == 'D')
									if (!used[i])
										printf("%c", str[i]);
							}
							printf("\n");
						}
					}
				} 
			}
		}
	}
	return 0;
}