function main(input) {
  let args = input.split(/\n|\s/);
  const isUpperCase = c => {
  return /^[A-Z]+$/g.test(c)
}
  if (isUpperCase(args[0])) {
    console.log('A');
  } else {
    console.log('a');
  }
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));