from datetime import datetime


def unixts_to_dt_obj(unixts):
    """
    Convert unix timestamp to naive datetime object in UTC time zone.

    :param float/int/str unixts: unix timestamp
    :returns: datetime object in UTC timezone
    """
    if isinstance(unixts, str):
        try:
            unixts = int(unixts)
        except ValueError:
            unixts = float(unixts)
    if isinstance(unixts, float):
        unixts = int(unixts)
    assert isinstance(unixts, int)
    return datetime.utcfromtimestamp(unixts)