PROGRAMMING:Polynomial evaluation
Enter a positive integer n to find the value of the following polynomial.
$$1^{2}-2^{2}+3^{2}-4^{2}+...+n^{2}$$
###Input format:
Enter a positive integer.
###Output format:
The value of a polynomial.
###Input example:
```in
twenty
```
###Output example:
```out
-210
```
answer：If there is no answer, please comment
$$1^{2}-2^{2}+3^{2}-4^{2}+...+n^{2}$$
###Input format:
Enter a positive integer.
###Output format:
The value of a polynomial.
###Input example:
```in
twenty
```
###Output example:
```out
-210
```
answer：If there is no answer, please comment