PROGRAMMING:Sfy grade conversion
SF seniors need to be stratified when they count students' grades at the end of the term. It's too troublesome to look at them one by one. It's better if they can get it directly. Smart acmer, help SF seniors. 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.
###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 "score is error!"
###Input example:
Here is a set of inputs. For example:
```in
-5
ninety-eight
```
###Output example:
The corresponding output is given here. For example:
```out
Score is error!
A
```
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 "score is error!"
###Input example:
Here is a set of inputs. For example:
```in
-5
ninety-eight
```
###Output example:
The corresponding output is given here. For example:
```out
Score is error!
A
```
answer：If there is no answer, please comment