''' Purpose: demonstrate a primitive 'random' digit generator
'''

SCALAR = 3141592653589793 * 2718281828459045 * 16180339887

# set the seed of the black box based on the length of what the user supplies
reply = input( 'Enter something: ' ) 

seed = ( len( reply ) + 1 ) * 7

# generate initial value from which to grab the 'random' digit
s = seed * SCALAR

s = str( s )

# store the generated digits in digits
digits = []

# let's generate 20 digits
for i in range( 0, 20 ) :

    # grab and save the middle digit of s
    n = len( s )
    d = s [ n // 2 ]
    d = int( d )

    digits.append( d )

    # generate a new s by first decomposing it into thirds
    a = s[ 0          : n // 3     ]
    b = s[ n // 3     : 2 * n // 3 ]
    c = s[ 2 * n // 3 :            ]

    # get rid of leading and trailing 0's of the thirds
    a = a.strip( '0' )
    b = b.strip( '0' )
    c = c.strip( '0' )
    
    # convert the thirds into int's
    a = int( a )
    b = int( b )
    c = int( c )

    # new s is initially the product of thirds times the SCALAR
    s = ( a * b * c * SCALAR )
    
    # convert product to a string
    s = str( s )

    # to keep process manageable hang onto only the middle fifty characters of s
    n = len( s )
    s = s[ n // 2 - 25 : n // 2 + 25 ]

# let's see what we got
print()

print( digits )