First Missing Packet

A streaming client is receiving data packets representing byte ranges [start, end). You know the total file size is S bytes (the file covers range [0, S)). Given the list of received byte ranges, identify the very first byte index that is missing and has not been received yet. If the entire file is complete from [0, S), print 'COMPLETE'. Input Format: First line: Two integers S (total size) and N (number of packets). Next N lines: Two integers 'start' and 'end' (exclusive end). Output Format: The integer index of the first missing byte, or 'COMPLETE'. Example: Input: 100 3 0 10 20 30 10 15 Output: 15 (Bytes 0-14 are covered, but 15 is missing.)