D

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

int main() {
    int t;
    cin>>t;

    while(t--){
        int n;
        cin>>n;

        vector<vector<int>> tree(n);

        for(int i=0; i<n-1; i++)
        {
            int u, v;
            cin>>u>>v;

            u--, v--;

            tree[u].push_back(v);
            tree[v].push_back(u);
        }

        vector<int> dist(n), prev(n);

        function<void(int, int)> DFS = [&](int u, int p)
        {
            prev[u] = p;
            for(auto v: tree[u])
            {
                if(v == p)      continue;
                dist[v] = 1+dist[u];
                DFS(v, u);
            }
        };


        DFS(0, -1);

        int x = max_element(dist.begin(), dist.end()) - dist.begin();

        dist[x] = 0;

        DFS(x, -1);

        int y = max_element(dist.begin(), dist.end()) - dist.begin();

        int r=0, b=0;

        string ans = "";
        for(int i=0; i<n; i++)      ans += '.';

        int cnt = dist[y]+1;
        cnt /= 2;

        while(y != -1)
        {
            if(cnt)         ans[y] = 'R', r++, cnt--;
            else            ans[y] = 'B', b++;

            y = prev[y];
        }

        for(int i=0; i<n; i++)
        {
            if(ans[i] != '.')       continue;

            if(r <= b)      ans[i] = 'R', r++;
            else            ans[i] = 'B', b++;
        }

        cout<<ans<<"\n";
    }
}