#include<stdio.h>
int main(){
  char n[3];
  scanf("%s",n);
  if(n[0]=='A' && n[1]=='B' && n[2]=='C')
    printf("ARC");
  else if(n[0]=='A' && n[1]=='R' && n[2]=='C')
    printf("ABC");
  return 0;
}
