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## 1142. Relations

Time limit: 1.0 second
Memory limit: 64 MB

### Background

Consider a specific set of comparable objects. Between two objects a and b, there exits one of the following three classified relations:
a = b
a < b
b < a
Because relation '=' is symmetric, it is not repeated above.
So, with 3 objects (a, b, c), there can exist 13 classified relations:
a = b = c       a = b < c       c < a = b       a < b = c
b = c < a       a = c < b       b < a = c       a < b < c
a < c < b       b < a < c       b < c < a       c < a < b
c < b < a

### Problem

Given N, determine the number of different classified relations between N objects.

### Input

Includes many integers N (in the range from 2 to 10), each number on one line. Ends with −1.

### Output

For each N of input, print the number of classified relations found, each number on one line.

inputoutput
```2
3
-1
```
```3
13
```
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