const Main = (input) => {
  const tmp = input.trim()

  let result = ''

  if (tmp === 'ABC') {
    result = 'ARC'
  } else if (tmp === 'ARC') {
    result = 'ABC'
  }

  console.log(result)
  return result
}

Main(require('fs').readFileSync('/dev/stdin', 'utf8'))