def main():
    with open('data.txt', 'r') as file:
        data = file.readlines()
        numbers = [int(line.strip()) for line in data if line.strip().isdigit()]
    sorted_numbers = sorted(numbers)

    with open('output.txt', 'w') as outfile:
        for number in sorted_numbers:
            outfile.write(f"{number}\n")

if __name__ == '__main__':
    main()