Problem:
Score : 200 points

Problem Statement

A sequence a=\{a_1,a_2,a_3,......\} is determined as follows:

The first term s is given as input.

Let f(n) be the following function: f(n) = n/2 if n is even, and f(n) = 3n+1 if n is odd.

a_i = s when i = 1, and a_i = f(a_{i-1}) when i > 1.

Find the minimum integer m that satisfies the following condition:

There exists an integer n such that a_m = a_n (m > n).

Constraints

1 \leq s \leq 100

All values in input are integers.

It is guaranteed that all elements in a and the minimum m that satisfies the condition are at most 1000000.

Input

Input is given from Standard Input in the following format:

s

Output

Print the minimum integer m that satisfies the condition.

Sample Input 1

8

Sample Output 1

5

a=\{8,4,2,1,4,2,1,4,2,1,......\}. As a_5=a_2, the answer is 5.

Sample Input 2

7

Sample Output 2

18

a=\{7,22,11,34,17,52,26,13,40,20,10,5,16,8,4,2,1,4,2,1,......\}.

Sample Input 3

54

Sample Output 3

114

Solution in Haskell (GHC 7.10.3) (judge verdict: Accepted)


import Control.Monad.Trans.State (get, modify, evalState)
import qualified Data.Map.Strict as M

f n
  | even n = div n 2
  | odd  n = 3 * n + 1

solv s = flip evalState (M.fromList [(s,1)]) $ go 2 s where
  go i prev = do
    let next = f prev
    m <- get
    case M.lookup next m of
      Just _ -> return i
      Nothing -> do
        modify (M.insert next i)
        go (i+1) next

main = do
  s <- read <$> getLine :: IO Int
  print $ solv s