An $nn$ table $a$ is defined as follows:

The first row and the first column contain ones, that is: $a_{i,1}=a_{1,i}=1$ for all $i=1,2,$dots,$n.$

Each of the remaining numbers in the table is equal to the sum of the number above it and the

number to the left of it$.$ In other words, the remaining elements are defined by the formula

$a_{i,j}=a_{i-1,j}+a_{i,j-1}.$

These conditions define all the values in the table.

You are given a number $n.$ You need to determine the maximum value in the $nn$ table defined by the

rules above.

Input

The only line of input contains a positive integer $n(1n10)-$ the number of rows and columns of

the table.

Output

Print a single line containing a positive integer $m-$ the maximum value in the table.