function Main(input) {
  input = input.replace(/\n/g, ' ');
  input = input.split(" ");
  var A = input[0];
  const isUpperCase = c => {
    return /^[A-Z]+$/g.test(c)
  }
  if(isUpperCase(A)){
    console.log("A");
  }else{
    console.log("a");
  }
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));