Evaluating Mathematical Expressions

You are given a string S which represents a mathematical expression. The expression contains only positive integers, addition (+) and subtraction (-) operators. Whitespaces may appear anywhere in the string and should be ignored.

Your task is to compute the value of the expression.

In mathematical terms, if the expression is processed as:

\( total = \sum_{i=1}^{n} (sign_i \times number_i) \)

where sign is determined by the preceding operator (default is positive), then total should be computed accordingly.

If the input string is empty or contains only whitespace, the result is 0.

inputFormat

The input consists of a single line from stdin which is the expression string S. This string may include spaces, digits, and the operators '+' and '-'.

outputFormat

Output a single integer which is the result of evaluating the expression. The output should be written to stdout.

3+2-1

4