How to write EXPRESSION for main contours in Mapfile?

Question

I'm working with mapfile. I defined new layer "contours" and I want to render with maxscale = 100000 and minscale = 50000 contours with value distance of 50. That means that I want in that scale render only those countours with values of "height" attribute of 0, 50, 100, 150, 200, 250, 300, 350.. etc.

LAYER
 NAME "contours"
 TYPE line
 STATUS off
 DATA "contours.shp"

 CLASS
 NAME "all_contours"
   STYLE
     COLOR 176 226 255
   END



  #Is this CLASS I started creating correct? 

   CLASS
       NAME "main_contours"
       MAXSCALE 99000
       MINSCALE 50000
       EXPRESSION #this is my question

   END
END

Answer 1

That should work using modulo:

EXPRESSION ( ([height] % 50) = 0 )