Title Description
There are n children, each child has its own seat. Just sit in the wrong seat every child the way how many?
n <= 66
Enter a description:
Line 1, a natural number and represents the number of children.
Output Description:
Output An integer that represents qualified sitting method How many?
Written encountered, Staggered equation: Dn = (n-1) (Dn-1 + Dn-2).