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

#define int long long
#define all(x) (x).begin(),(x).end()
#define pb push_back


typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;
typedef vector<pii> vpii;
vi C;
vvi G;
void DFS(int u){
    for(auto v:G[u])if(!C[v]){
        C[v]=3-C[u];
        DFS(v);
    }
}


void problem()
{
    int n, m;
    cin >> n >> m;
    C.assign(n,0);
    G.assign(n,vi());
    for(int i=0;i<n;i++){
        G[i].pb({(i+1)%n});
        G[(i+1)%n].pb({i});
    }
    for(int i=0;i<m;i++){
        int a,b;cin>>a>>b;
        G[a].pb(b);
        G[b].pb(a);
    }
    C[0]=1;
    DFS(0);
    for(auto a:C){
        if(a==1){
            cout<<"R";
        }else{
            cout<<"B";
        }
    }

}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int tc;
    cin>>tc;
    while(tc--){
        problem();
        cout<<"\n";
    }
   
}