import argparse
from colorsys import hls_to_rgb, rgb_to_hls
import sys

# setting up arguments
parser = argparse.ArgumentParser(
    description='Function that outputs a pleasant text color hex '
                'given a background color hex')
parser.add_argument('color', help='Color in #xxxxxx or xxxxxx format')

args = parser.parse_args()
color = args.color

# removing #
if color.startswith('#'):
    color = color[1:]

# splitting, converting to decimal and then to 0-1 range
try:
    r, g, b = [int(color[i:i+2], 16) / 255.0 for i in range(0, len(color), 2)]
except ValueError:
    print 'Wrong color supplied'
    sys.exit()

# shifting
h, l, s = [(i + 0.5) % 1 for i in rgb_to_hls(r, g, b)]

# converting back to rgb
result = [format(int(i*255), 'x') for i in hls_to_rgb(h, l, s)]
print '#{}'.format(''.join(result))