#include<bits/stdc++.h>
#define ios ios::sync_with_stdio(0),cin.tie(0),cout.tie(0)
using namespace std;using ll = long long;using PLL = pair<ll,ll>;
const ll MAX = 1e18;const ll MIN = -1e18;const ll INF=0x3f3f3f3f;
const ll Q = 2e5+9;const ll MOD = 1e9 + 7;
pair<ll,ll> f[5];ll n,m;
bool check(){
    ll x=0,y=0;
    if(x==n and y==m) return false;
    for (ll i = 1; i <= 4; i++)
    {
        ll now=0;
        while(f[i].second==1 and now<f[i].first) {
            x++,now++;
            if(x==n and y==m) return false;
        }
        while(f[i].second==-1 and now<f[i].first) {
            x--,now++;
            if(x==n and y==m) return false;
        }
        while(f[i].second==2 and now<f[i].first) {
            y--,now++;
            if(x==n and y==m) return false;
        }
        while(f[i].second==-2 and now<f[i].first) {
            y++,now++;
            if(x==n and y==m) return false;
        }
    }
    return true;
}
void solve(){
   cin>>n>>m;
   string s;cin>>s;
   f[1].first=0;
   f[2].first=0;
   f[3].first=0;
   f[4].first=0;
   f[1].second=-1;
   f[2].second=1;
   f[3].second=-2;
   f[4].second=2;
   for (ll i = 0; i < s.size(); i++)
   {
    if(s[i]=='L') f[1].first++;
    if(s[i]=='R') f[2].first++;
    if(s[i]=='U') f[3].first++;
    if(s[i]=='D') f[4].first++;
   }
   do
   {
    if(check()){
        for (ll i = 1; i <= 4; i++)
        {
        ll now=0;
        while(f[i].second==1 and now<f[i].first) {
            cout<<'R';now++;
        }
        while(f[i].second==-1 and now<f[i].first) {
            cout<<'L';now++;
        }
        while(f[i].second==2 and now<f[i].first) {
            cout<<'D';now++;
        }
        while(f[i].second==-2 and now<f[i].first) {
            cout<<'U';now++;
        }
        }
        cout<<"\n";
        return;
    }
   } while (next_permutation(f+1,f+5));
   cout<<"Impossible\n";
}
int main(){
    ios;ll _=1;cin>>_;
    while (_--)solve();
    return 0;
}