#include <bits/stdc++.h>
using namespace std;
#define SZ 1234567
int T,n,m;
void sol() {
    scanf("%d%d",&n,&m);
    int ans=2e9,U=0;
    for(int i=1;i<=m;++i) {
        int u,v;
        scanf("%d%d",&u,&v);
        int d=(v-u+n)%n;
        if((u-v+n)%n<d) swap(u,v);
        d=(v-u+n)%n;
        if(d<ans) ans=d,U=u;
    }
    for(int i=0;i<n;++i)
        printf("%c","BR"[(i-U-1+n)%n%2]);
    printf("\n"); 
}
int main() {
    scanf("%d",&T);
    while(T--) sol();
}