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

#define N 5

int main(){
  char S[N];
  char abc = "ABC";
  char arc = "ARC";
  scanf( "%s", S );

  if ( strcmp( S, abc ) == 0 ){
    printf( "%s\n", arc );
  }else{
    printf( "%s\n", abc );
  }
  
  return 0;
  
}