"""
Write a command-line program that prints out the sum of two non-negative integers as input arguments.
You must not use any built-in BigInteger library or convert the inputs to integer directly.
"""
def parseStrToInt(strNum):
    num = 0
    for char in strNum:
        next = num * 10 + ord(char) - ord('0')
        num = next

    return num

def sumAB(number1, number2):
    if (type(number1) == 'int' and type(number2) == 'int'):
        return number1 + number2
    else:
        return 'Invalid input.'

print('Please enter two non-negative integers:')

A = parseStrToInt(input('number 1:'))
B = parseStrToInt(input('number 2:'))

result = sumAB(A,B)

print('Result: ', result)