#include<iostream>
using namespace std;

const int MAXN = 2 * 1e5 + 5;
const int MAXM = 2 * 1e5 + 5;

struct node{
	int to, next, id;
}e[MAXM << 1];
int h[MAXN], tot = 0;
void add(int x, int y, int id){
	e[++ tot] = {y, h[x], id};
	h[x] = tot;
}
int n, m;
char col[MAXN];
bool vis[MAXN], v2[MAXN];

void dfs(int now, bool op){
	vis[now] = 1;
	for(int i = h[now];i;i = e[i].next){
		int v = e[i].to, id = e[i].id;
		if(vis[v]) continue;
		col[id] = (op) ? 'B' : 'R';
		dfs(v, !op);
	}
}

int main(){
	freopen("paintoads.in", "r", stdin);
	freopen("paintoads.out", "w", stdout);
	cin.tie(0) -> ios::sync_with_stdio(0);
	cin >> n >> m;
	for(int i = 1;i <= m;i ++){
		int u, v; cin >> u >> v;
		add(u, v, i); add(v, u, i);
	}
	for(int i = 1;i <= m;i ++) col[i] = 'G';
	for(int i = 1;i <= n;i ++){
		if(!vis[i]) dfs(i, 0);
	}
	for(int i = 1;i <= m;i ++){
		cout << col[i];
	}
	cout << '\n';
	return 0;
}