module kkk
  sub main ()
    dim s as string
    dim alp as string
    dim ans as string
    
    s = Console.ReadLine()
    
    alp = "abcdefghijklmnopqrstuvwxyz"
    
    ans = Right(Left(alp, InStr(alp, s) + 1), 1)
    
    Console.WriteLine(ans)
  end sub
end module
    