#include<bits/stdc++.h>
constexpr int maxn = 2e5 + 10, maxm = 5e5 + 10;
std::vector<std::pair<int, int> > to[maxn];
int st[maxm];
void dfs(int u) {
   if (to[u].empty()) return ;
   auto [v, w] = to[u].back(); to[u].pop_back();
   if (st[w]) dfs(u);
   else st[w] = u, dfs(v);
}
inline void solve() {
   int n, m;
   scanf("%d%d", &n, &m);
   int l = 0;
   for (int i = 1; i <= n + m + 1; i++) to[i].clear();
   for (int i = 1, f; i < n; i++) {
      scanf("%d", &f), st[++l] = 0;
      to[i].emplace_back(f, l), to[f].emplace_back(i, l);
   }
   for (int i = 1, f; i < n; i++) {
      scanf("%d", &f), st[++l] = 0;
      to[n + i].emplace_back(n + f, l), to[n + f].emplace_back(n + i, l);
   }
   int pl = l + 1;
   for (int i = 1; (int)to[i].size() == 1; i++) {
      st[++l] = 0;
      to[i].emplace_back(n + i, l), to[n + i].emplace_back(i, l);
   }
   int pr = l;
   for (int i = 1; i <= n + m; i++) {
      if (to[i].size() % 2 == 1) {
         st[++l] = 0;
         to[i].emplace_back(n + m + 1, l), to[n + m + 1].emplace_back(i, l);
      }
   }
   assert(to[n + m + 1].size() % 2 == 0);
   for (int i = 1; i <= n + m; i++) dfs(i);
   for (int i = pl; i <= pr; i++) {
      putchar("RB"[st[i] <= n]);
   }
   puts("");
}
int main() {
   for (int T, _ = scanf("%d", &T); T--; ) {
      solve();
   }
   return 0;
}