PROGRAMMING:1/(1+2+3+...+n)
Enter N and evaluate the following expression.
###Input format:
Enter a positive integer directly. There are no additional characters
###Output format:
Directly output the real result with 6 decimal places. There are no additional characters.
###Input example:
```in
ten
```
###Output example:
```out
one point eight one eight one eight two
```
answer：If there is no answer, please comment
###Input format:
Enter a positive integer directly. There are no additional characters
###Output format:
Directly output the real result with 6 decimal places. There are no additional characters.
###Input example:
```in
ten
```
###Output example:
```out
one point eight one eight one eight two
```
answer：If there is no answer, please comment