PROGRAMMING:C programming experiment 2-2-1

If else statement programming, according to the input of the hundred score (integer), converted to the corresponding five score grade output.
When 90 ≤ score ≤ 100, grade = a;
When 80 ≤ score < 90, grade = B;
When 70 ≤ score < 80, grade = C;
When 60 ≤ score < 70, grade = D;
When 0 ≤ score < 60, grade = E.
If score < 0 or score > 100 is input, "input error!" is output.
###Input format:
Enter a percentage score (integer).
###Output format:
Output corresponding level. When the input score is unreasonable, the prompt message "input error!" will be output.
###Input example:
```in
eighty-five
```
###Output example:
```out
B
```
###Input example:
```in
one hundred and twenty
```
###Output example:
```out
Input error!
```







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