import Foundation
var a: String = readLine()!

let pattern = "[a-z]"

let regex = try? NSRegularExpression(pattern: "[a-z]", options: NSRegularExpression.Options())
if regex!.firstMatch(in: a, options: NSRegularExpression.MatchingOptions(), range: NSMakeRange(0, 1)) != nil {
    print("a")
} else {
    print("A")
}