$ ghci
GHCi, version 6.12.1: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Loading package ffi-1.0 ... linking ... done.i
Prelude> let f n = if n == 1 then 1 else if even n then f (n `div` 2) else f (3 * n + 1);;
Prelude> f 10
1
Prelude> f 100
1
Prelude> f 1000
1
Prelude> f 1001
1
Prelude> f 1010101
1
Prelude> f 12345
1
Prelude> f 1111111111111111111111111
1
Prelude> f 11111111111111111111111111111111111111111111119
1
Prelude> f 111111111111111111111111111111111111111111111121
1
