def get_symmetric_vertex(vertex_index, sym_table_list):
    """
    Returns symmetric vertex or -1 if not symmetric vertex found
    :param vertex_index: int
    """
    for i in range(len(sym_table_list)):
        if int(vertex_index) == int(sym_table_list[i]):
            if i % 2 == 0:
                sym_vtx = sym_table_list[i + 1]
            else:
                sym_vtx = sym_table_list[i - 1]
            break
    return sym_vtx
