# File: sumdigits.py
# compute and print the sum of the digits of a number
#
# Matt Bishop, ECS 10, Fall 2012
#

#
# sum the digits in n
#
def sumdigit(n):
    # base case: single digit, return its value
    if n < 10:
        return n
    # recursive case: several digits, grab the right one and
    # add it to the sum of the rest
    return (n % 10) + sumdigit(n // 10)

#
# the main routine
#
def main():
    # read in the number
    try:
        n = int(input("A non-negative, preferably multidigit, integer please: "))
    except:
        print("I said an integer!")
        return

    # check for error
    if n < 0:
        print("I said non-negative!")
        return

    # print the result!
    print("The sum of the digits in", n, "is", sumdigit(n))

main()