def checkio(number):

    binary = "{0:b}".format(number)
    return binary.count('1')


#These "asserts" using only for self-checking and not necessary for auto-testing
if __name__ == '__main__':
    assert checkio(4) == 1
    assert checkio(15) == 4
    assert checkio(1) == 1
    assert checkio(1022) == 9
