def find_corrupt(vcs, revs, corrupt):
    """
    Find first corrupt section and return its index
    :param vcs: GridVCS instance
    :param revs: List of Revision
    :param corrupt: Corrupted index (zero-based) or None if not corrupted
    :return:
    """
    for n, rev in enumerate(revs):
        if rev.id in corrupt:
            return n
    return None