PROGRAMMING:Maximum value problem

Input no more than 40 non negative integers from the keyboard. When the input value is negative, it means the end of input. Try to program out the maximum value.
###Input format:
Give no more than 40 non negative integers (space separated) on a line, ending with a negative number.
###Output format:
Output the maximum value in the form of output sample
###Input example:
```in
9 0 62 36 15 28 -1
```
###Output example:
```out
max=62
```
###Input example:
```in
-1
```
###Output example:
```out
max=-1
```






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