import re


def parse_header(line):
    """Extract header data"""
    match = re.match(r'%START Version: (\d+) (\w+) (\d+)-(\d+)', line)
    if not match:
        return None

    header = {
        "version": int(match.group(1)),
        "source": match.group(2),
        "serials": (int(match.group(3)), int(match.group(4))),
    }
    return header