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#<Xsize> = 50
#<Ysize> = 50
#<XStep> = 5
#<YStep> = 5

#<XgridSize> = 0
#<YgridSize> = 0

#1 = 0
#2 = 0

M101
g90 g0 x0y0

O100 while [#1 LT [#<Ysize>]]
    #2 = 0
    g0 x0 y[#1]
    M100
    O101 while [#2 LT [#<Xsize>]]
        #2 = [#2+#<XStep>]
        g0 x[#2]
        M100
        O102 if [ #1 EQ 0 ]
            #<XgridSize> = [#<XgridSize>+1]
        O102 endif
    O101 endwhile
    #1 = [#1+#<YStep>]
    #<YgridSize> = [#<YgridSize>+1]
O100 endwhile

(DEBUG, #<XgridSize> by #<YgridSize>)

%