Collatz Conjecture

The Collatz conjecture which is also known as the 3n+1 conjecture is a very well known and old conjecture in mathematics. The conjecture is as follows. Take any natural number $n$. If $n$ is even, divide it by two to get $n/2$ and if $n$ is odd number greater than $1$, triple it and add one to obtain 3n+1. Repeat this process to get a sequence of natural numbers known as the Hailstone sequence. The conjecture is that no matter what number you start, you always reach $1$.

The hailstone sequence for n = 3 is 3, 10, 5, 16, 8, 4, 2, 1. Paul Erdos said "Mathematics is not yet ripe for such problems" and offered $500 for its solution. Now it's time to show Erdos that the Collatz conjecture can be proved for small numbers in $11$-th Iran Internet Programming Contest. You are to write a program that computes the length of the Hailstone sequence for the given $n$.