#include <bits/stdc++.h>

using namespace std;

const int N = 2e5 + 5;

vector<int> G[N];
int dis[N];

signed main() {
    int T; scanf("%d", &T);
    while (T--) {
        int n, m; scanf("%d%d", &n, &m);
        for (int i = 1; i <= n; ++i) G[i].clear();
        for (int i = 1; i <= n; ++i) G[i].push_back(i % n + 1), G[i % n + 1].push_back(i);
        while (m--) {
            int x, y; scanf("%d%d", &x, &y);
            ++x, ++y;
            G[x].push_back(y);
            G[y].push_back(x);
        }
        memset(dis, 0, sizeof(dis));
        dis[1] = 1;
        queue<int> Q; Q.push(1);
        while (!Q.empty()) {
            int x = Q.front(); Q.pop();
            for (auto v : G[x]) if (!dis[v]) {
                dis[v] = dis[x] + 1;
                Q.push(v);
            }
        }
        for (int i = 1; i <= n; ++i) {
            putchar("BR"[dis[i] & 1]);
        }
        puts("");
    }
    return 0;
}