#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#define N 100005

using namespace std;

int mx,my;
int n;
char s[N];
int L,R,D,U;
char tmp[4] = {'U','D','L','R'};

bool check(){
    int stx = 0,sty = 0;
    for(int i = 0;i < n;i ++){
        if(stx == mx && sty == my) return false;
        if(s[i] == 'U') sty ++;
        if(s[i] == 'D') sty --;
        if(s[i] == 'L') stx --;
        if(s[i] == 'R') stx ++;
        if(stx == mx && sty == my) return false;
    }
    return true;
}

void solve(){
    L = R = D = U = 0;
    scanf("%d%d",&mx,&my);
    scanf("%s",s);
    n = strlen(s);

    for(int i = 0;i < n;i ++)
        if(s[i] == 'U') U ++;
        else if(s[i] == 'L') L ++;
        else if(s[i] == 'R') R ++;
        else if(s[i] == 'D') D ++;

    sort(tmp,tmp + 4);
    do{
        int cnt = 0;
        for(int i = 0;i < 4;i ++){
            if(tmp[i] == 'U'){
                for(int j = 0;j < U;j ++)
                    s[cnt++] = 'U';
            }
            else if(tmp[i] == 'D'){
                for(int j = 0;j < D;j ++)
                    s[cnt++] = 'D';
            }
            else if(tmp[i] == 'L'){
                for(int j = 0;j < L;j ++)
                    s[cnt++] = 'L';
            }
            else if(tmp[i] == 'R'){
                for(int j = 0;j < R;j ++)
                    s[cnt++] = 'R';
            }
        }
        s[cnt] = '\0';
        if(check()){
            printf("%s\n",s);
            return;
        }
    }while(next_permutation(tmp,tmp + 4));
    puts("Impossible");
}

int main(){
    int T;scanf("%d",&T);
    while(T --)
        solve();
    return 0;
}