Strange people live in Moscow! Each time in the bus, getting a ticket with a 6-digit number, they try to sum up the first half of digits and the last half of digits. If these two sums are equal, they suppose such a ticket to be a lucky one. A person, who owns the lucky ticket, should dream about something, eat the ticket (no, it’s not made of chocolate, it’s made of paper!) and the dream will come true… At least, they believe it!

Strange people live in St.Petersburg! Each time in the bus, getting a ticket with a 6-digit number, they try to sum up the digits on the odd positions and the digits on the even positions. If these two sums are equal, they suppose such a ticket to be a lucky one. A person, who owns the lucky ticket, should dream about something, eat the ticket (no, even in St. Petersburg lucky tickets are not made of chocolate, they’re made of paper!) and the dream will come true… At least, they believe it!

In the "third Russian capital" — Yekaterinburg — we laugh about such strange ideas. We are practical. We are not superstitious, even a little bit. But we understand that too much luck cannot be good. Thus we consider every ticket, which is lucky both in "Moscow sense" and "St. Petersburg sense" to be unlucky. If we get an unlucky ticket in the bus, we throw it away and leave the bus immediately! Two examples of unlucky tickets are 472175 and 810513.

You are to write a program, which calculates the total number of unlucky *N*-digit tickets.

### Input

The input contains a single even positive integer *N* (2 ≤ *N* ≤ 20) — the number of digits in the ticket. Please note, that, for example 00742544 is a valid 8-digit ticket (by the way, it is a St.Petersburg-style lucky ticket).

### Output

Your program should output a single integer number — the total number of unlucky *N*-digit tickets.

### Sample

**Problem Author: **Leonid Volkov

**Problem Source: **The Seventh Ural State University collegiate programming contest