#include <iostream>
#include <cstdio>
#include <vector>
using namespace std;
const int N=2e5+10;
int f[N],n,m,col[N],vis[N];
int ver[N],to[N<<1],nxt[N<<1],idx,id[N<<1];
int found(int x){
	return f[x]==x?x:f[x]=found(f[x]);
}
void add(int x,int y,int i){
	to[++idx]=y,nxt[idx]=ver[x],ver[x]=idx,id[idx]=i;
}
void dfs(int x,int c){
	vis[x]=1;
	for(int i=ver[x];i;i=nxt[i]){
		int y=to[i];
		if(vis[y])continue;
		col[id[i]]=3-c;
		dfs(y,3-c);
	}
	return;
}
int main(){
	freopen("paintoads.in","r",stdin);
	freopen("paintoads.out","w",stdout);
	scanf("%d %d",&n,&m);
	for(int i=1;i<=n;i++)f[i]=i;
	for(int i=1,u,v,a,b;i<=m;i++){
		scanf("%d %d",&u,&v);
		add(u,v,i),add(v,u,i);
	}
	for(int i=1;i<=n;i++){
		if(!vis[i])dfs(i,1);
	}
	for(int i=1;i<=m;i++){
		if(col[i]==1)printf("R");
		if(col[i]==2)printf("B");
		if(col[i]==0)printf("G");
	}
	return 0;
}