Spiral surface intersect on top

Hi freinds! i am trying to make spiral tower and use loft surface option, but in the end point surface intersect each other. is there way to make it differnt lenght? or make leng of loft not same as on bottom?!
Spiral work.gh (9.5 KB)

You didn’t internalise the curve in your grasshopper file.

Right-click on Curve component and choose Internalise data


my apologise
Spiral work.gh (22.3 KB)