100 def fna(a)
 ? a
 for y = 0 to 10 : a = a * 2 : next
 gosub 230
 fna = 23 * a
 fnend
 ? x
 input "x? "; x
 gosub 200
 goto 220
200 ? fna(x), x
 return
220 end
230 return