import math


class Vector2D:
    def __init__(self, x: float = 0, y: float = 0):
        self.x = x
        self.y = y

    def __add__(self, other):
        return Vector2D(self.x + other.x, self.y + other.y)

    def __sub__(self, other):
        return Vector2D(self.x - other.x, self.y - other.y)

    def __mul__(self, other):
        if isinstance(other, (int, float)):
            num = other
            return Vector2D(self.x * num, self.y * num)
        elif isinstance(other, Vector2D):  # kinda scalar_product()
            return Vector2D(self.x * other.x, self.y * other.y)
        raise ValueError

    def __str__(self) -> str:
        return f"Vector2D({self.x}, {self.y})"

    def __len__(self) -> int:
        return int(math.sqrt(self.x ** 2 + self.y ** 2))

    def __eq__(self, other) -> bool:
        return self.x == other.x and self.y == other.y

    def add(self, vector) -> None:
        self.x += vector.x
        self.y += vector.y

    def sub(self, vector) -> None:
        self.x -= vector.x
        self.y -= vector.y

    def mul(self, num) -> None:
        self.x *= num
        self.y *= num

    def cos(self, other) -> float:
        return float(
            (self.x * other.x + self.y * other.y) / len(self) * len(other)
        )


def main():
    vector1 = Vector2D()
    vector2 = Vector2D(1, 3)
    vector3 = Vector2D(6, 66)

    print(vector1 + vector2)
    vector1.add(vector3)
    print(vector1)

    print(vector1 - vector2)
    vector1.sub(vector3)
    print(vector1)

    num = 5.7289314718
    print(vector2 * num)
    vector2.mul(num)
    print(vector2)

    print(len(vector2))

    print(vector2 * vector3)

    print(vector2.cos(vector3))

    print(vector2 == vector3)


if __name__ == "__main__":
    main()