#include<stdio.h>
#include<string.h>

int main(void){
  char txt[3];

  scanf("%s",txt);
  if(0==strcmp(txt,"ABC"))
    printf("ARC\n");
  else if(0==strcmp(txt,"ARC"))
    printf("ABC\n");
  else
    printf("error\n");
  return 0;
}
  