"use strict";

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