"use strict";

const main = (arg) => {
  if (/^[A-Z]+$/g.test(arg)) {
    console.log("A");
  } else {
    console.log("a");
  }
};
main(require("fs").readFileSync("/dev/stdin", "utf8"));
// main("z");
//https://atcoder.jp/contests/abc171/tasks/abc171_a
