/*
Things to notice:
1. do not calculate useless values
2. do not use similar names
 
Things to check:
1. submit the correct file
2. time (it is log^2 or log)
3. memory
4. prove your naive thoughts 
5. long long
6. corner case like n=0,1,inf or n=m
7. check if there is a mistake in the ds or other tools you use
8. fileio in some oi-contest

9. module on time 
10. the number of a same divisor in a math problem
11. multi-information and queries for dp and ds problems
*/
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
const int mod=998244353;
const int inf=0x3f3f3f3f;
int n,m,K;
vector <int> g[100005],h[100005],G[100005];
int col[100005],lef[100005];
set <int> S[100005];
void dfs1(int u)
{
	if(!g[u].size()) 
	{
		S[u].insert(u);
		K=max(K,u);
		return;
	}
	for(int i=0;i<g[u].size();i++)
	{
		int v=g[u][i];
		dfs1(v);
		if(S[v].size()) 
		{
			S[u].insert(*S[v].begin());
			if(S[u].size()==2)
			{
				int x=(*S[u].begin()),y=(*prev(S[u].end()));
				G[x].pb(y),G[y].pb(x);
				S[u].clear();
			}
		}
	}
}
void dfs2(int u)
{
	if(!h[u].size()) 
	{
		S[u].insert(u);
		return;
	}
	for(int i=0;i<h[u].size();i++)
	{
		int v=h[u][i];
		dfs2(v);
		if(S[v].size()) 
		{
			S[u].insert(*S[v].begin());
			if(S[u].size()==2)
			{
				int x=(*S[u].begin()),y=(*prev(S[u].end()));
				G[x].pb(y),G[y].pb(x);
				S[u].clear();
			}
		}
	}
}
void dfs3(int u,int co)
{
	col[u]=co;
	for(int i=0;i<G[u].size();i++) if(col[G[u][i]]==-1) dfs3(G[u][i],co^1);
}
void solve()
{
	cin>>n>>m;
	for(int i=1;i<=max(n,m);i++) col[i]=-1,lef[i]=1,g[i].clear(),h[i].clear(),G[i].clear();
	for(int i=1;i<n;i++)
	{
		int x;
		cin>>x;
		g[x].pb(i);
	}
	for(int i=1;i<m;i++)
	{
		int y;
		cin>>y;
		h[y].pb(i);
	}
	K=0;
	for(int i=1;i<=n;i++) S[i].clear();
	dfs1(n);
	for(int i=1;i<=m;i++) S[i].clear();
	dfs2(m);
	for(int i=1;i<=K;i++) if(col[i]==-1) dfs3(i,0);
	for(int i=1;i<=K;i++) cout<<(col[i]==0?"R":"B");
	cout<<"\n";
}
signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	int _=1;
	cin>>_;
	while(_--) solve();
	return 0;
}