19. Commitments and contingencies: (a) Leases DOCOMO leases certain facilities and equipment under capital leases or operating leases. Assets covered under capital leases as of March 31, 2016 and 2017 were as follows: Millions of yen Class of property 2016 2017 Machinery, vehicles and equipment  5,027  4,801 Less: Accumulated depreciation and amortization (3,333 ) (2,839 ) Total  1,694  1,962 Future minimum lease payments by year under capital leases together with the present value of the net minimum lease payments as of March 31, 2017 were as follows: Years ending March 31 Millions of yen 2018  1,074 2019 787 2020 525 2021 346 2022 174 Thereafter 13 Total minimum lease payments 2,919 Less: Amount representing interest (86 ) Present value of net minimum lease payments 2,833 Less: Amounts representing estimated executory costs (379 ) Net minimum lease payments 2,454 Less: Current obligation (861 ) Long-term capital lease obligations  1,593 The above obligations are classified as part of Other current liabilities and Other long-term liabilities as appropriate. The minimum lease payments required under operating leases that have initial or remaining non-cancellable lease terms in excess of one year as of March 31, 2017 were as follows: Years ending March 31 Millions of yen 2018  12,126 2019 9,418 2020 6,245 2021 4,697 2022 4,147 Thereafter 19,511 Total minimum lease payments  56,144 Total rental expense for all operating leases except those with terms of 1 month or less that were not renewed for the fiscal years ended March 31, 2015, 2016 and 2017 were as follows: Millions of yen 2015 2016 2017 Rental expense  79,634  77,208  77,696 (b) Litigation DOCOMO is involved in litigation and claims arising in the ordinary course of business. DOCOMO believes that none of the litigation or claims outstanding, pending or threatened against DOCOMO would have a material adverse effect on DOCOMOs results of operations, financial position or cash flows. (c) Purchase commitments DOCOMO has entered into various contr