#include <stdio.h>

int main(void){
  char S[4];
  char R[4]="ARC";
  char B[4]="ABC";
  int i;

  scanf("%s",&S);

  if(!strcmp(S,"ARC")){
printf("ABC");
  }
  else if(!strcmp(S,"ABC")){
printf("ARC");
  }
  return 0;
}