X1, x2, x3... , xn is set {1, 2, 3,... , n} a permutation, arranged in reverse order of logarithmic called reverse number, (such as 1432 number of reverse order is 3, or three to reverse, respectively is: 43,42,32), is when the x3=4 (number 3 to 4), the number of all the reverse order of arrangement and for how much? (n=6, is the 2020 national high school mathematics league of zhejiang division preliminaries question fills up the topic 10)

Input format:
Enter a n,

The output format:
Output the number of reverse order and,

Input the sample:

6
The output sample:

912