#include <bits/stdc++.h>
using namespace std;

void solve() {
	int n, m; cin >> n >> m;
	vector<vector<int>> g(n);
	for (int i = 0; i < n-1; i++) {
		int j; cin >> j; j--;
		g[i].push_back(j);
		g[j].push_back(i);
	}
	for (int i = 0; i < m-1; i++) {
		int j; cin >> j;
	}

	int k = 0;
	for (int i = 0; i < n-1; i++) {
		if (g[i].size() == 1) k++;
		else break;
	}

	for (int i = 0; i < k; i++) {
		if (i % 2) cout << "B"; else cout << "R";
	}
	cout << '\n';
}

signed main() {
	ios::sync_with_stdio(0); cin.tie(0);
	
	int t; cin >> t;
	while (t--) {
		solve();
	}
	
	return 0;
}