#include<bits/stdc++.h>
using namespace std;
struct DSU {
	vector<int> e;
	DSU(int N) { e = vector<int>(N, -1); }

	// get representive component (uses path compression)
	int get(int x) { return e[x] < 0 ? x : e[x] = get(e[x]); }

	bool same_set(int a, int b) { return get(a) == get(b); }

	int size(int x) { return -e[get(x)]; }

	bool unite(int x, int y) {  // union by size
		x = get(x), y = get(y);
		if (x == y) return false;
		if (e[x] > e[y]) swap(x, y);
		e[x] += e[y]; e[y] = x;
		return true;
	}
};
int main(){
    int t;
    cin >> t;
    while(t--){
        int n, m;
        cin >> n >> m;
        vector<int> p(n - 1);
        int k = n;
        for(int i = 0; i < n - 1; i++){
            cin >> p[i];
            p[i]--;
            k = min(k, p[i]);
        }
        vector<int> q(m - 1);
        for(int i = 0; i < m - 1; i++){
            cin >> q[i];
            q[i]--;
        }
        DSU dsu(k * 2);
        vector<int> thing(n, -1);
        for(int i = 0; i < k; i++){
            thing[i] = i;
        }
        for(int i = 0; i < n - 1; i++){
            if(thing[i] != -1){
                if(thing[p[i]] == -1){
                    thing[p[i]] = thing[i];
                }
                else{
                    int u = thing[i];
                    int v = thing[p[i]];
                    thing[v] = -1;
                    dsu.unite(2 * u, 2 * v + 1);
                    dsu.unite(2 * u + 1, 2 * v);
                }
            }
        }
        vector<int> thing2(m, -1);
        for(int i = 0; i < k; i++){
            thing2[i] = i;
        }
        for(int i = 0; i < m - 1; i++){
            if(thing2[i] != -1){
                if(thing2[q[i]] == -1){
                    thing2[q[i]] = thing2[i];
                }
                else{
                    int u = thing2[i];
                    int v = thing2[q[i]];
                    thing2[v] = -1;
                    dsu.unite(2 * u, 2 * v + 1);
                    dsu.unite(2 * u + 1, 2 * v);
                }
            }
        }
        for(int i = 0; i < k; i++){
            if(dsu.get(2 * i) % 2 == 1){
                cout << "R";
            }
            else{
                cout << "B";
            }
        }
        cout << "\n";
    }
}