#include<cstdio>
#include<vector>
#include<queue>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<ctime>
#include<random>
#include<assert.h>
#define pb emplace_back
#define mp make_pair
#define fi first
#define se second
#define dbg(x) cerr<<"In Line "<< __LINE__<<" the "<<#x<<" = "<<x<<'\n'
#define dpi(x,y) cerr<<"In Line "<<__LINE__<<" the "<<#x<<" = "<<x<<" ; "<<"the "<<#y<<" = "<<y<<'\n'
#define DE(fmt,...) fprintf(stderr, "Line %d : " fmt "\n",__LINE__,##__VA_ARGS__)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int>pii;
typedef pair<ll,int>pli;
typedef pair<ll,ll>pll;
typedef pair<int,ll>pil;
typedef vector<int>vi;
typedef vector<ll>vll;
typedef vector<pii>vpii;
typedef vector<pll>vpll;
template<typename T>T cmax(T &x, T y){return x=x>y?x:y;}
template<typename T>T cmin(T &x, T y){return x=x<y?x:y;}
template<typename T>
T &read(T &r){
	r=0;bool w=0;char ch=getchar();
	while(ch<'0'||ch>'9')w=ch=='-'?1:0,ch=getchar();
	while(ch>='0'&&ch<='9')r=r*10+(ch^48),ch=getchar();
	return r=w?-r:r;
}
template<typename T1,typename... T2>
void read(T1 &x,T2& ...y){read(x);read(y...);}
const int mod=998244353;
inline void cadd(int &x,int y){x=(x+y>=mod)?(x+y-mod):(x+y);}
inline void cdel(int &x,int y){x=(x-y<0)?(x-y+mod):(x-y);}
inline int add(int x,int y){return (x+y>=mod)?(x+y-mod):(x+y);}
inline int del(int x,int y){return (x-y<0)?(x-y+mod):(x-y);}
int qpow(int x,int y){
	int s=1;
	while(y){
		if(y&1)s=1ll*s*x%mod;
		x=1ll*x*x%mod;
		y>>=1;
	}
	return s;
}
const int N=200010;
int n,m;
int fa[N],siz[N],vis[N],tot,ot[N],ok[N],cur[N];
vi eg[N];
vpii tr[N];
void dfs1(int x){
	if(!eg[x].size()){
		if(x<=n){
			++tot;ot[x]=tot;vis[tot]=0;
			tr[x].pb(x+n,tot);
			tr[x+n].pb(x,tot);
		}
		siz[x]=1;
	}
	for(auto v:eg[x])dfs1(v),siz[x]+=siz[v];
	if(siz[x]&1){
		++tot;vis[tot]=0;
		tr[x].pb(fa[x],tot);
		tr[fa[x]].pb(x,tot);
	}
}
void dfs2(int x){
	ok[x]=1;
	for(int &i=cur[x];i<(int)tr[x].size();i++){
		int v=tr[x][i].fi,id=tr[x][i].se;
		if(!vis[id]){
			vis[id]=x;
			dfs2(v);
		}
	}
}
void solve(){
	read(n,m);
	for(int i=1;i<=n+m+1;i++)vi().swap(eg[i]),vpii().swap(tr[i]),ot[i]=ok[i]=cur[i]=siz[i]=0;
	for(int i=1;i<n;i++)read(fa[i]);
	fa[n]=n+m+1;
	for(int i=n+1;i<n+m;i++)read(fa[i]),fa[i]+=n;
	fa[n+m]=n+m+1;
	for(int i=1;i<=n+m;i++)eg[fa[i]].pb(i);
	tot=0;
	dfs1(n+m+1);
	for(int i=1;i<=n+m+1;i++)
		if(!ok[i])
			dfs2(i);
	for(int i=1;i<=n;i++)if(ot[i])putchar(vis[ot[i]]<=n?'R':'B');
	puts("");
}
signed main(){
	#ifdef do_while_true
//		assert(freopen("data.in","r",stdin));
//		assert(freopen("data.out","w",stdout));
	#endif
	int T;read(T);
	while(T--)solve();
    #ifdef do_while_true
//		cerr<<'\n'<<"Time:"<<1.0*clock()/CLOCKS_PER_SEC*1000<<" ms"<<'\n';
	#endif
	return 0;
}