import math


def find_gcd(numbers: set[int]) -> int:
    """Return the greatest common divisor of all the given numbers.

    Preconditions:
        - len(numbers) >= 2

    Hints:
        - Use the math module's gcd function to calculate the gcd of two numbers.
        - Use an accumulator to store the gcd of the numbers seen so far.
        - For all ints x, gcd(x, 0) = x.
        - For all ints a, b, c, the gcd of all three numbers is equal to gcd((gcd(a, b), c).
          That is, you can calculate the gcd of a and b first, then calculate the gcd of
          that number and c.

    >>> find_gcd({18, 12})
    6
    >>> find_gcd({121, 99, -11, 0})
    11
    """
    temp = numbers.copy()
    gcd = temp.pop()
    for n in temp:
        gcd = math.gcd(gcd, n)
    return gcd