def s( d ) :
    ''' Solves the sigma.s() homework 24 problem description
    '''

    # Nested For Loop Way
    answer = 0     # Initialize an accumulator to 0
    for row in d: # row is each smaller list in d
        # print(row)
        for element in row: # Look at each number in each smaller list
            answer = answer + element # Add each number in each smaller list to answer
    return answer

    # You can't use sum on the element in the second for loop because element is a
    # single element so you don't want to call sum(1) or something on a 1 in a smaller
    # list.

    # answer = 0
    # for row in d:     # Loop through each row (smaller list)
    #     answer = answer + sum( row )  # Add the sum of each smaller list to our answer
    # return answer

    answer = 0
    for row in d:   # Loop throw each smaller list in d
        row_sum = sum( row )    # Get the sum of the smaller list because we can call sum( list )
        answer = answer + row_sum   # Add the row sum to our accumulator
    return answer

    # Don't name your variables after built in function/keywords!
    # Don't call variables list or sum or max etc. because those
    # are keywords!

    # Remember sum( list ) returns the sum of numbers in a list
    # answer = sum( d )   # Keep in mind that dataset is a list of lists, not a list of integers!
                        # You can't just call sum( dataset ) - it can't see the numbers
                        # inside this way.
    # You cannot call sum ( list ) on a single number either!
    # x = sum(12) will not work!



''' DO NOT MODIFY THE BELOW CODE '''
    
if ( __name__ == '__main__' ) :
    import sigma

    d1 = [ [ 0 ],             [ 1, 2 ],             [ 1, 2, 3 ], [ 0 ]       ]
    d2 = [ [ 1, 0, 1, 2, 2 ], [ 3, 0, 1, 1, 1, 0 ], [ 2 ],       [ 0, 0, 1 ] ]
    d3 = [ [ 3, 0, 3],        [ 3, 0, 3, 0, 1],     [ 1, 0, 2 ]              ]
    d4 = [ ]


    s1 = s( d1 );       print( 's( d1 ) =', s1 )
    s2 = sigma.s( d2 );       print( 's( d2 ) =', s2 )
    s3 = sigma.s( d3 );       print( 's( d3 ) =', s3 )
    s4 = sigma.s( d4 );       print( 's( d4 ) =', s4 )