function main(arg) {
  var str = arg.trim();
  if (str == "ABC") {
    console.log("ARC");
    return;
  } else if (str == "ARC") {
    console.log("ABC");
    return;
  }
}
main(require("fs").readFileSync("/dev/stdin", "utf8"));
//https:/ / atcoder.jp / contests / abc166 / tasks / abc166_a;
