You have a magical calculator that can undo operations you don't want. This calculator supports the following three operations:
- + x: Add x to the current result.
- - x: Subtract x from the current result.
- Undo: Undo the previous addition or subtraction operation. If there was no previous addition or subtraction, no action is taken.
please ouput the result of the calculator after n operation.
The calculator starts the calculation from 0.
the first line contain one integer n.
the next n lines, each line contain one of the 3 operations.
- 1 ≤ n ≤ 2 * 106
- 1 ≤ x ≤ 100
Output the result of the calculator.
Remember to print a ‘\n’ at the end of the output.