Problem 42686. What's the missing interior angle?

I'm talking about polygons... The sum of the interior angles of a triangle is 180 degrees. The sum of the interior angles of a quadrilateral is 360 degrees, and so on.

For this problem, you are given n-1 angles (in degrees) of an n-sided polygon. Please return the final angle.

Triangle examples:

>>a=missing_interior_angle([60 60])
a =
    60
>>a=missing_interior_angle([45 45])
a =
    90