Rooks on a chessboard#1327

Rooks on a chessboard

1 second

128 megabytes

Medium

Since childhood, little Garik was curious about one question: in how many ways can $n$ rooks be placed on a chessboard of size $n \times n$ n \times n so that they do not attack each other? He spent a long time solving this puzzle for each case; and when he finally solved it, he gave up chess.

How quickly can you solve this problem?

Input

The size of the chessboard $n$ ( $n \leq 1000$ n \le 1000).

Output

Print the answer found by Garik.

Examples

Example 1

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n \times n

n \leq 1000