PROGRAMMING:Find the value of 1 * 2 + 2 * 3 +... + 20 * 21
Find the value of the following expression.
###Output format:
The calculation results are directly output in one line without any additional characters.
###Output example:
```out
three thousand and eighty
```
answer：If there is no answer, please comment
###Output format:
The calculation results are directly output in one line without any additional characters.
###Output example:
```out
three thousand and eighty
```
answer：If there is no answer, please comment