montyHall(n) ==
  wd:=[1+random(3) for j in 1..n]
  fc:=[1+random(3) for j in 1..n]
  st:=reduce(_+,[1 for j in 1..n | wd.j=fc.j])
  p:=(st/n)::DoubleFloat
  FORMAT(nil,"stay: ~A, switch: ~A",p,1-p)$Lisp