PROGRAMMING:Grade conversion
When the score of the hundred point system is converted to the five level scoring system, the score above 90 is a, 80-89 is B, 70-79 is C, 60-69 is D, and 0-59 is e（ It is recommended to use switch statement to complete)
###Input format:
There are several groups of tests, and each group enters an integer score. Process to the end of input.
###Output format:
Output the character level corresponding to the score line by line. If score is illegal, output "error!"
###Input example:
Here is a set of inputs. For example:
```in
one
sixty-one
one hundred and two
```
###Output example:
The corresponding output is given here. For example:
```out
E
D
error!
```
answer：If there is no answer, please comment
###Input format:
There are several groups of tests, and each group enters an integer score. Process to the end of input.
###Output format:
Output the character level corresponding to the score line by line. If score is illegal, output "error!"
###Input example:
Here is a set of inputs. For example:
```in
one
sixty-one
one hundred and two
```
###Output example:
The corresponding output is given here. For example:
```out
E
D
error!
```
answer：If there is no answer, please comment