from typing import List
import math


def checkio(a: int, b: int, c: int) -> List[int]:
    """
    α = arccos[(b² + c² − a²) ÷ 2bc]
    β = arccos[(a² + c² − b²) ÷ 2ac]
    γ = arccos[(a² + b² − c²) ÷ 2ab]
    """
    try:
        alpha = round(math.degrees(math.acos((b ** 2 + c ** 2 - a ** 2) / (2 * b * c))))
        beta = round(math.degrees(math.acos((a ** 2 + c ** 2 - b ** 2) / (2 * a * c))))
        gamma = round(math.degrees(math.acos((a ** 2 + b ** 2 - c ** 2) / (2 * a * b))))
        angles = [alpha, beta, gamma]
        angles.sort()
        if angles[0] == 0:
            return [0, 0, 0]

        return angles
    except ValueError:
        return [0, 0, 0]


# These "asserts" using only for self-checking and not necessary for auto-testing
if __name__ == '__main__':
    print("Example:")
    print(checkio(4, 4, 4))

    assert checkio(4, 4, 4) == [60, 60, 60], "All sides are equal"
    assert checkio(3, 4, 5) == [37, 53, 90], "Egyptian triangle"
    assert checkio(2, 2, 5) == [0, 0, 0], "It's can not be a triangle"
    assert checkio(10, 20, 30) == [0, 0, 0], "It's can not be a triangle"
    print("Coding complete? Click 'Check' to earn cool rewards!")