1. Theory Lab HK, Huawei Tech. Investment Co., Limited, Shatin, N. T., Hong Kong
Department of Mathematics, Beijing Jiaotong University, Beijing, China, 100044
2. Theory Lab HK, Huawei Tech. Investment Co., Limited, Shatin, N. T., Hong Kong
3. Theory Lab HK, Huawei Tech. Investment Co., Limited, Shatin, N. T., Hong Kong
Center of Discrete Mathematics, Fuzhou University, Fujian, China, 350108