The Redacted Project Timeline

An engineer has a list of active project periods [start, end]. However, the company went through a 'blackout' period [B_start, B_end] where all work is considered void. Find the total number of valid work hours. Valid hours are hours spent in project periods that do not overlap with the blackout period. Input Format: - Line 1: N (number of project periods). - Next N lines: start and end of each period. - Last line: B_start and B_end of the blackout. Output Format: - Total valid work hours (integer). Example: Input: 2 10 20 25 35 15 30 Output: 10 (Explanation: Project 1 [10,20] minus blackout [15,30] = [10,15] (len 5). Project 2 [25,35] minus blackout [15,30] = [30,35] (len 5). Total 10.)