PROGRAMMING:prime number again

Enter a positive integer n to determine whether it is a prime.
###Input format:
There are several groups of test data, which are processed to the end of the file, and a number n (2 < = n < = 10000) is input each time.
###Output format:
If it is a prime number, output yes; if it is not a prime number, output No.
###Input example:
Here is a set of inputs. For example:
```in
two
three
eight
```
###Output example:
The corresponding output is given here. For example:
```out
YES
YES
NO
```







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