# Write a function that takes no parameters,
# and repeatedly asks for a single capital letter
# from the user until the user enters one.
# The function should return that letter.
# Each time a user enters an invalid character,
# print an error message.

# built in ord('c') and chr(int) are useful


#https://en.wikipedia.org/wiki/ASCII

def valid_let():

    char = raw_input("Enter capital")
    while char < 'A' or char > 'Z':
        print 'Invalid'
        char = raw_input("Enter again")

    return char