#include<bits/stdc++.h>
using namespace std;
constexpr int maxn=2e5+5;
vector<int> e[maxn];
int col[maxn];  
inline void solve(){
    int n,m;cin>>n>>m;
    for(int i=1;i<=n;i++) e[i].clear(),col[i]=-1;
    for(int i=1,u,v;i<=m;i++) cin>>u>>v,e[u].push_back(v),e[v].push_back(u);
    for(int i=1;i<=n;i++) e[i].push_back(i%n+1),e[i%n+1].push_back(i);
    queue<int> q;q.push(1);col[1]=0;
    while(!q.empty()){
        int p=q.front();q.pop();
        for(auto x:e[p]) if(!~col[x]) col[x]=col[p]^1,q.push(x);
    }
    for(int i=1;i<=n;i++) cout<<"BR"[col[i]];cout<<'\n';
}
int main(){
    int t;cin>>t;
    while(t--) solve();
}