PROGRAMMING:A simple calculator
Simulate the work of simple arithmetic unit. Suppose that the calculator can only carry out addition, subtraction, multiplication and division operations. The number of operations and results are integers. The priority of the four operators is the same, and they are calculated from left to right.
###Input format:
Input in a line to give a four arithmetic, no spaces, and at least one operands. If the "equal sign" = "is met, it indicates the end of input.
###Output format:
Output the result of an expression in one line, or output the error message "error" if the division denominator is 0 or there is an illegal operator.
###Input example:
```in
1+2*10-10/2=
```
###Output example:
```out
ten
```
answer：If there is no answer, please comment
###Input format:
Input in a line to give a four arithmetic, no spaces, and at least one operands. If the "equal sign" = "is met, it indicates the end of input.
###Output format:
Output the result of an expression in one line, or output the error message "error" if the division denominator is 0 or there is an illegal operator.
###Input example:
```in
1+2*10-10/2=
```
###Output example:
```out
ten
```
answer：If there is no answer, please comment