#include <stdio.h>

int main() {
  char str;
  char a, b;
  
  a = "ABC";
  b = "ARC";
  scanf("%s", &str);
  
  if(str == "ABC") {
    printf("%s\n", b);
  } else if(str == "ARC") {
    printf("%s\n", a);
  } else {
    return 0;
  }
}