function main(input){
  input = input.trim();
  var dai = ["A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"];
  // var syou = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
  var answer = "";
  if(dai.includes(input)>0){
    answer = "A";
  }else{
    answer = "a";
  }
  console.log(answer);
}
main(require("fs").readFileSync("/dev/stdin","utf8"));