Gas tank capacity: 20 Gallons

Test case

Initially no gas in the tank

Station Si	Pi: Gas price per gallon at station Si	Gi: Number of gallons needed to go from Si to Si+1
S0	$3	5
S1	$2	3
S2	$1	6
S3	$4	4
S4	$1	5
S5	$3	8
S6	$2	13
S7	$1	2
S8	$3	1
S9	$2	5
S10