We lease 462 retail sites from third parties under certain non-cancelable operating leases that expire from time to time through 2041. The weighted-average remaining lease term was 5.6 years as of December 31, 2021.

Lease expense was classified in the statement of income as follows (in thousands):

	Year Ended December 31,
	2021		2020		2019
Cost of sales	$	23,765	$	25,214	$	27,493
Operating expenses		13,531		9,067		379
General and administrative expenses		1,331		1,081		685
Total	$	38,627	$	35,362	$	28,557

Variable lease payments based on inflation or fuel volume included in the table above totaled $3.4 million, $2.3 million and $1.8 million for 2021, 2020 and 2019, respectively. Short-term lease payments included in the table above that are excluded from the lease liability amounted to $1.7 million, $0.8 million and $0.6 million for 2021, 2020 and 2019, respectively. Cash paid for amounts included in the measurement of lease liabilities under operating leases totaled $33.5 million, $33.1 million and $25.8 million for 2021, 2020 and 2019, respectively.

As of December 31, 2021, future minimum rental payments under operating leases, excluding variable lease payments or short-term payments, were as follows (in thousands). The weighted-average discount rate as of December 31, 2021 was 6.2 %.

2022		36,041
2023		33,691
2024		30,540
2025		28,180
2026		24,092
Thereafter		68,812
Total future payments		221,356
Less impact of discounting		46,375
		174,981
Current portion		34,832
Long-term portion	$	140,149

Most lease agreements include provisions for renewals. We generally do not include renewal options in our lease term for purposes of measuring our lease liabilities and right-of-use assets unless the sublease to our customer extends beyond the term of the head lease.

See Note 4 for information regarding the acquisition of leasehold interests in connection with the acquisition of retail and wholesale assets.

Of our leased sites, we operate 124 of them as company operated sites. Substantially all the remaining leased sites are subleased to lessee dealers or commission agents under leases with terms generally ranging from one to ten years and which may include renewal options. Sublease rental income amounted to $34.5 million, $34.8 million and $38.2 million for 2021, 2020 and 2019, respectively.

Motor fuel stations are leased to tenants under operating leases with various expiration dates ranging through 2037. Most lease agreements include provisions for renewals. We generally do not include renewal options in our lease term. Future minimum rental payments under non-cancelable operating leases with third parties as of December 31, 2021 were as follows (in thousands):

2022		50,189
2023		39,783
2024		33,130
2025		25,792
2026		17,262
Thereafter		33,339
Total future minimum lease payments	$	199,495

The future minimum rental payments presented above do not include contingent rent based on future inflation, future revenues or volumes of the lessee, or non-lease components for amounts that may be received as tenant reimbursements for certain operating costs.

Deferred rent income from straight-line rent relates to the cumulative amount by which straight-line rental income recorded to date exceeds cash rents billed to date under the lease agreement and totaled $5.1 million and $5.3 million at December 31, 2021 and 2020, respectively.