PROGRAMMING:1+1/(1*2)+1/(2*3)+1/(3*4)
Find the sum of the first 20 terms of the following expression.
###Output format:
Directly output the result with 2 decimal places, without any additional format and characters.
###Output example:
```out
one point nine five
```
answer：If there is no answer, please comment
###Output format:
Directly output the result with 2 decimal places, without any additional format and characters.
###Output example:
```out
one point nine five
```
answer：If there is no answer, please comment