Movement
Consider the following strange game. There is a 1×2n board with cells numbered 1..2n from left to right. Each of the first n cells is occupied by a token. All other cells are initially empty.
Alice and Bob move one by one: each move consists in choosing a token such that the right neighboring cell is unoccupied and moving the token to this empty cell. The player who can't make a move loses the game.
Having played thousands of games, Alice and Bob made a really unexpected conjecture: the result of the game depends only on n. But they are not sure about this. So they decided to check each possible sequence of moves for some n. Each play lasts for 1 minute. Your task is to calculate time it will take Alice and Bob to verify the conjecture.
Input
One line containing an integer 1 ≤ n ≤ 30.
Output
Write one integer — time in minutes.