Mr SKW deeply wants his students to love SMAT in its entirety. He wants his students to enjoy every epsilon and delta that the course has to offer, however, he is strict and methodical. He hates students who write unbalanced parenthesis strings.

The definition of a balanced parenthesis string is :
1. If a string S is stable, then {S} is also stable.
2. If S and T are both stable, then ST (the concatenation of the two) is also stable.

All of these strings are balanced: {}, {}{}, and {{}{}}; But none of these: }{, {{}{, nor {}{.

Mr. SKW now asks you to find the number of balanced strings of length n. Complete this task to avoid a back and become the apple of his eyes :P

Input Format
The first and only line of input contains the integer n < 30.

Output Format
Print the number of balanced parenthesis strings of length n.

Problem Setter - Dhvit