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Problems

Movement

Movement

Time limit 1 second
Memory limit 64 MiB

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 data

One line containing an integer 1n30.

Output data

Write one integer — time in minutes.

Examples

Input example #1
2
Output example #1
2