Sensor Bridge

A motion sensor records active intervals [start, end]. However, the sensor is flaky: if the gap between two active intervals is less than or equal to G, we assume the sensor should have been active during the gap and 'bridge' them. Calculate the total duration of the final active intervals after bridging. Example: Input: N=2, G=10 Intervals: [10, 20], [25, 35] Gap is 5 (<= 10), so bridge to [10, 35]. Total duration 25.