#include <bits/stdc++.h>
using namespace std;
#define int long long
//#define endl "\n"
#define PII pair<int,int>
#define PIS pair<int,string>
#define fr(i,x,y) for(int i=x,p=y;i<=p;i++)
#define rp(i,x,y) for(int i=x,p=y;i>=p;i--)
const int N=1e6+10;
const int M=1e2+10;
int mod=998244353;
int a[N];
int f[M][M];
int xx,yy;
int n,m;
string s;
int d[4];
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
void dfs(int x,int y,int step){
    if(step==s.size()){
        return;
    }
    fr(i,0,3){
        if(!d[i])continue;
        x+=dx[i];
        y+=dy[i];
        if(x==n&&y==m){
            continue;
        }
        d[i]--;
        if(i==0)cout<<"R";
        if(i==1)cout<<"U";
        if(i==2)cout<<"L";
        if(i==3)cout<<"D";
        dfs(x,y,step+1);
        return;
    }
}
void solve(){
    
    
    cin>>n>>m;
    fr(i,0,3){
        d[i]=0;
    }
    cin>>s;
    fr(i,0,s.size()-1){
        if(s[i]=='L')d[2]--;
        if(s[i]=='R')d[0]++;
        if(s[i]=='U')d[1]++;
        if(s[i]=='D')d[3]--;
    }
    
    if(n==0&&m==0){
        cout<<"Impossible"<<endl;
        return;
    }
    int cnt=0,now;
    int f[4]={0};
    fr(i,0,3){
        if(d[i]!=0&&!f[i]){
            cnt++;
            f[i]=1;
            now=i;
        }
    }
    int x=0,y=0;
    if(cnt==1){
        if(now%2==0){
            if(m==0&&(n>=min(0ll,d[now])&&n<=max(0ll,d[now]))){
                cout<<"Impossible"<<endl;
                return;
            }else{
                cout<<s<<endl;
                return;
            }
        }
        else{
            if(n==0&&(m>=min(0ll,d[now])&&m<=max(0ll,d[now]))){
                cout<<"Impossible"<<endl;
                return;
            }else{
                cout<<s<<endl;
                return;
            }
        }
    }
    fr(i,0,3){
        if(i%2==0)x+=d[i];
        else y+=d[i];
    }
    if(x==n&&y==m){
        cout<<"Impossible"<<endl;
        return;
    }
    fr(i,0,3){
        if(d[i]<0){
            d[i]=-d[i];
        }
    }
    dfs(0,0,0);
    cout<<endl;
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0),cout.tie(0);
    int n=1;
    cin>>n;
    while(n--)
    solve();
    return 0;
}