"use strict";

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