int m=1000000007;
int n,t;
char s[1010];

int f(int i,int x){
	int y,r;
	if(i==0) return 0;
	y=s[i-1]-'A';
	if(x==y){
		r=f(i-1,x);
	}else{
		r=f(i-1,3-x-y);
		r=(r+t)%m;
	}
	t=t*2%m;
	return r;
}

main(){
	scanf("%d %s",&n,s);
	t=1;
	printf("%d\n",f(n,0));
}