from typing import IO
from io import StringIO


def input_stream() -> IO:
    """Input stream fixture."""
    return StringIO(
        """1 + 2 * 3 + 4 * 5 + 6
1 + (2 * 3) + (4 * (5 + 6))
2 * 3 + (4 * 5)
5 + (8 * 3 + 9 + 3 * 4 * 3)
5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))
((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2
((6))"""
    )