def find_min_radius(feasible, eps=1e-6, max_radius=None):
    if max_radius is None:
        high_bound = 1.0
        while not feasible(high_bound):
            high_bound *= 2
            if high_bound > 1e10:
                raise ValueError(
                    "Не удалось найти верхнюю границу. Возможно, feasible всегда возвращает False."
                )
        low = 0.0
        high = high_bound
    else:
        low = 0.0
        high = max_radius

    while high - low > eps:
        mid = (low + high) / 2.0

        if feasible(mid):
            high = mid
        else:
            low = mid

    return high


def can_cover(points, m, r):
    if not points:
        return True

    used_circles = 0
    i = 0

    while i < len(points):
        circle_center = points[i] + r
        circle_right = circle_center + r

        used_circles += 1
        if used_circles > m:
            return False

        while i < len(points) and points[i] <= circle_right:
            i += 1

    return True


if __name__ == "__main__":
    print("Введите N и M через пробел:")
    n, m = map(int, input("> ").split())

    print(f"Введите {n} координат точек (по одной на строке):")
    points = []
    for _ in range(n):
        point = float(input().strip())
        points.append(point)

    points.sort()

    def feasible(r):
        return can_cover(points, m, r)

    eps = 1e-6
    result = find_min_radius(feasible, eps=eps)

    print(f"Минимальный радиус: {result:.6f}")