Forbidden Strings

A string of letters $A,B$, $C$ is forbidden if there are three consecutive letters from which one is $A$, one is $B$ and one is $C$. For example, $BAACAACCBAAA$ is forbidden, while $AABBCCAABB$ is not.

How many such strings of length $n$ are not forbidden?

Input

Each line contains one number $n(1\le n\le 30)$.

Output

For each input value of $n$ print in a separate line the number of strings of length $n$ are not forbidden.

Examples