"use strict";

function main(input) {
  input = input.trim();
  const isUpperCase = (c) => {
    return /^[A-Z]+$/g.test(c);
  };
  if (isUpperCase(input)) {
    console.log("A");
  } else {
    console.log("a");
  }
}

main(require("fs").readFileSync("/dev/stdin", "utf-8"));
