Problem statement.
The input file contains at most 100 brackets (characters '(', ')', '[' and ']') that are situated on a single line without any other characters among them.


I've used scanf("%s",str) and got WA#13 many times!
Then I dicided to read input by character and got Accepted!

The test data of #13 is a blank line，it is not break the rule of the input specification..
Mean while, scanf("%s", str) statement can't read in a blank line...