#!/usr/bin/env python3
import csv
import json
import sys

if __name__ == "__main__":
    json_list = json.load(sys.stdin)
    if not isinstance(json_list, list):
        print("JSON object is not a list.", file=sys.stderr)
        sys.exit(1)
    if len(json_list) == 0:
        print("JSON list is empty.", file=sys.stderr)
        sys.exit(1)
    keys = set()
    for element in json_list:
        if isinstance(element, dict):
            keys |= element.keys()
        else:
            print("Non-dict element:", element, file=sys.stderr)
            sys.exit(1)
    writer = csv.DictWriter(sys.stdout, fieldnames=list(keys))
    writer.writeheader()
    for element in json_list:
        writer.writerow(element)