const input = require("fs").readFileSync("/dev/stdin", "utf8");
// const input = 'ARC';

function Main(input) {
  let isABC = input === 'ABC' ? true:false;
  if (isABC){
    console.log('ARC')
    return
  }
  console.log('ABC')
}

// Don't edit this line!
Main(input);