Evaluate Mathematical Expression

You are given a string representing a mathematical expression. The expression contains non-negative integers, the addition operator (+), the subtraction operator (-), and may include spaces. Your task is to evaluate the expression and output the result.

The expression adheres to the following format: \(number \; [+, -] \; number \; [+, -] \; number \; ...\). Operators are processed sequentially from left to right (i.e. no operator precedence is applied), and there are no parentheses in the expression.

inputFormat

A single line from standard input containing the mathematical expression.

outputFormat

A single integer printed to standard output, which is the result of evaluating the expression.## sample

10 + 20 - 5 + 3

28