#include<bits/stdc++.h>
#define int long long
#define pii pair<int, int>
#define ll long long
using namespace std;
const int maxn = 2e5 + 10;
vector<pii> G[maxn];
char ans[maxn];
int col[maxn];
void dfs(int u, int f) {
    for (auto [w, v] : G[u]) {
        if (col[v] == -1) {
            col[v] = col[u] ^ 1;
            dfs(v, u);
        } 
    }
}
void solve() {
    int n, m; cin >> n >> m;
    for (int i = 0; i < n; i++) G[i].clear(), col[i] = -1;
    for (int i = 0; i < n; i++) {
        G[i].emplace_back(1, (i + 1) % n);
        G[(i + 1) % n].emplace_back(1, i);
    }
    while (m--) {
        int u, v; cin >> u >> v;
        G[u].emplace_back(0, v);
        G[v].emplace_back(0, u);
    }
    for (int i = 0; i < n; i++)
        sort(G[i].begin(), G[i].end());
    col[0] = 0;
    dfs(0, 0);
    for (int i = 0; i < n; i++)
        if (col[i] == 0) cout << 'B';
        else cout << 'R';
    cout << "\n";
}
signed main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;
    cin >> t;
    while (t--) solve();
    return 0;
}