#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define rd() ({long _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define rep(v,e) for(long v=0;v<e;++v)
#define rep3(v,s,e) for(long v=s;v<e;++v)

typedef unsigned long ulong;
char*mmap();
char wbuf[1<<25];

void radix_sort_aux(unsigned*a,unsigned*b,int n){
	int c[512];
	for(int i=0;i<512;++i){
		c[i]=0;
	}
	for(int i=0;i<n;++i){
		++c[a[i]&511];
	}
	int t=0;
	for(int i=0;i<512;++i){
		int u=c[i];
		c[i]=t;
		t+=u;
	}
	for(int i=0;i<n;++i){
		b[c[a[i]&511]++]=a[i]>>9|a[i]<<23;
	}
}

void radix_sort(unsigned*a,int n){
	static unsigned b[100000];
	radix_sort_aux(a,b,n);
	radix_sort_aux(b,a,n);
}

unsigned b[100000];

int main(){
	char*rp=mmap(0l,1l<<25,1,2,0,0ll);
	long n=rd();
	long k=rd();
	rep(i,k){
		long a=rd();
		long c=*rp;
		rp+=2;
		b[i]=c<<18|a;
	}
	radix_sort(b,k);
	char*wp=wbuf;
	long j=0;
	rep3(i,1,n+1){
		unsigned p='BGR';
		if(b[j]>>14==i){
			if((char)b[j]=='G'){
				p='BRG';
			}
			else
			if((char)b[j]=='B'){
				p='GRB';
			}
			++j;
		}
		++i;
		if(b[j]>>14==i){
			if((char)b[j]=='G'){
				if(p=='GRB') p='RGB';
			}
			else
			if((char)b[j]=='B'){
				if(p=='BRG') p='RBG';
				if(p=='BGR') p='GBR';
			}
			++j;
		}
		++i;
		if(b[j]>>14==i){
			++j;
		}
		*(unsigned*)wp=p;
		wp+=3;
	}

	write(1,wbuf,n);
	_exit(0);
}