def long_repeat(line: str) -> int:
    longest = 0
    """
        length the longest substring that consists of the same char
    """
    current = None
    current_counter = 0
    for char in line:
        if char != current:
            if current_counter > longest:
                longest = current_counter
            current = char
            current_counter = 1
        else:
            current_counter += 1

    if current_counter > longest:
        longest = current_counter
    return longest


if __name__ == '__main__':
    # These "asserts" using only for self-checking and not necessary for auto-testing
    assert long_repeat('sdsffffse') == 4, "First"
    assert long_repeat('ddvvrwwwrggg') == 3, "Second"
    assert long_repeat('abababaab') == 2, "Third"
    assert long_repeat('') == 0, "Empty"
    print('"Run" is good. How is "Check"?')