Subtraction of Oil between two difference dates

Hi all, I need the dax for this issue, please help.

I need to have the subtraction of oil between two dates. For example,

Oil on January 1      12

Oil on January  2      5

Oil on January 3       0

Oil on January 4      11

What is the diffrence between last day (January 4) and first day (January 1) =

(12+5+0+11) - 12 = 16