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

int main(void)
{
  char input[3];
  int cmpABC, cmpARC;
  
  gets(input);
  sscanf(input, "%s");
  
  cmpABC = strcmp(input, "ABC");
  cmpARC = strcmp(input, "ARC");
  
  if(cmpABC == 0)
  {
    printf("ABC\n");
  }
  else if(cmpARC == 0)
  {
    printf("ARC\n");
  }
  else
  {
  }
  
  return 0;
}