import Foundation

let input = readLine()!

let learge = ["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"]
let small = ["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"]
for i in 0...25 {
    if input == learge[i] {
        print("A")
    }
    if input == small[i] {
        print("a")
    }
}