Problems

# Playing with graph

# Playing with graph

Peter and Vasil are playing another good game. They have a sheet of paper, which shows the **n** circles labeled with numbers from **1** to **n**. Participants in turn draw arrows connecting the circles. In this case the arrow of **a** ring in a circle **b** allowed to hold if the following two conditions:

- there are no arrows from
**a**to**b**; - can not get the arrow from
**b**to**a**.

For example, at the left position we can put one of three arrows (shown at the right).

The loser is one who can not make a move.

Peter decided to write a program that plays in this game. To do this, he wants to first count how many different positions can come on a sheet.

Here are all **25** items from the condition.

#### Input

One integer **n** (**1** ≤ **n** ≤ **100**).

#### Output

Print the number of possible positions without leading zeros.

Input example #1

3

Output example #1

25