//Shirasu Azusa 2024.6
#include <bits/stdc++.h>
#define fi first
#define se second
#define eb emplace_back
#define mp make_pair
using namespace std;
typedef long double ld;
typedef long long ll;
typedef unsigned long long ull;
typedef __int128 i128;
template<class T,class S>
bool chmax(T &a,const S b) {return (a<b?a=b,1:0);}
template<class T,class S>
bool chmin(T &a,const S b) {return (a>b?a=b,1:0);}
int popcnt(int x) {return __builtin_popcount(x);}
int popcnt(ll x)  {return __builtin_popcountll(x);}
int topbit(int x) {return (x==0?-1:31-__builtin_clz(x));}
int topbit(ll x)  {return (x==0?-1:63-__builtin_clzll(x));}
int lowbit(int x) {return (x==0?-1:__builtin_ctz(x));}
int lowbit(ll x)  {return (x==0?-1:__builtin_ctzll(x));}

#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define per(i,a,b) for(int i=(a);i>=(b);i--)
typedef pair<int,int> pii;  
typedef vector<int> vi;
typedef vector<pii> vp;
typedef tuple<int,int,int> tiii;
int read() {
  int x=0,w=1; char c=getchar(); 
  while(!isdigit(c)) {if(c=='-') w=-1; c=getchar();}
  while(isdigit(c)) {x=x*10+(c-'0'); c=getchar();} 
  return x*w;
}

const int N=3e5+5;
int n,m,k,p[N],q[N],f[N],deg[N],g[N],tot,vst[N],r[N];
vp e[N];

void dfs(int u) {
  while(e[u].size()) {
    auto [v,d]=e[u][e[u].size()-1]; e[u].pop_back();
    if(vst[d]) continue;
    vst[d]=v+N; dfs(v);
  }
}

void work() {
  n=read(), m=read();
  rep(i,1,n) p[i]=f[i]=0;
  rep(i,1,m) q[i]=g[i]=0;
  rep(i,1,n) deg[i]=0;
  rep(i,1,n-1) p[i]=read(), deg[p[i]]++;
  int k=1; while(k<=n&&deg[k]==0) k++; k--;
  rep(i,1,m-1) q[i]=read();
  rep(i,1,k) f[i]=g[i]=1;
  rep(i,1,n) f[p[i]]+=f[i];
  rep(i,1,m) g[q[i]]+=g[i];
  tot=1;
  rep(i,1,n) if(f[i]&1) {
    ++tot; if(i<=k) r[i]=tot;
    e[p[i]].eb(i,tot), e[i].eb(p[i],tot);
  }
  rep(i,1,m) if(g[i]&1) {
    ++tot; int x=(i<=k?i:i+m);
    e[q[i]+m].eb(x,tot), e[x].eb(q[i]+m,tot);
  }
  rep(i,1,tot) vst[i]=0;
  rep(i,0,n+m) dfs(i);
  rep(i,1,k) {
    if(vst[r[i]]-N==i) putchar('R');
    else putchar('B');
  } puts("");
}


signed main() {
  int T=read(); while(T--) work();
  return 0;
}