function main(input) {
  const isUpperCase = (str) => {
    let arr = str.match(/^[A-Z]/);
    return arr ? true : false;
  };
  if (isUpperCase(input)) {
    console.log("A");
    return;
  } else {
    console.log("a");
    return;
  }
}
// main(require("fs").readFileSync("/dev/stdin", "utf8"));
main("A");
