function Main(input) {
	input = input.trim();
	var CAPITAL = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  	var small = "abcdefghijklmnopqrstuvwxyz";
	var ans;
  	if (input.indexOf(CAPITAL) === -1){
      ans = 'a';
    } else {
      ans = 'A';
    }
  	console.log(ans);
}   
Main(require("fs").readFileSync("/dev/stdin", "utf8"));