Code isn't pretty, but it's working 8)
(* filename: main.fs *)
open System
let _ =
let n = Console.ReadLine() in
if n <> "42" then
Printf.printf "%s\n" n
let mutable continueLooping = true
while continueLooping do
let v = Console.ReadLine()
if v = "42" then continueLooping <- false
else Printf.printf "%s\n" v
else Printf.printf ""